20 Considerations for Building a Hyperbaric Chamber

Building a hyperbaric chamber is a complex undertaking that must address safety, performance, and regulatory demands across various use cases, from clinical medical treatment (HBOT) to personal wellness, veterinary therapy, and research applications.

1. Structural Design and Materials for Pressure Containment

A hyperbaric chamber’s structure must safely withstand internal pressures above atmospheric levels without deformation or failure. Hard-shell chambers are typically constructed from high-strength metals (e.g. steel or aluminum alloys) with integrated acrylic viewports, all designed to meet pressure vessel codes. These rigid chambers often adhere to the ASME Pressure Vessels for Human Occupancy (PVHO-1) standard, which specifies material strength, weld quality, and safety factors for human-rated pressure vessels. Soft-shell (inflatable) chambers, by contrast, use reinforced polymer fabrics (such as PVC or polyurethane coated textiles) secured with zipper closures and external support straps. While soft chambers are lightweight and portable, their fabric materials limit the maximum safe pressure (typically ≲1.3 ATA). Soft chambers are not certified to ASME PVHO standards and can be prone to punctures or gradual material fatigue over time. Regardless of type, designers must select materials compatible with high oxygen environments (non-combustible, low off-gassing) and ensure the chamber’s shape (cylinder, rectangular, etc.) evenly distributes pressure loads. Proper structural engineering and quality manufacturing are paramount – an over-pressurized chamber can catastrophically fail if design limits are exceeded. In summary, the chamber’s hull and viewports should be built with proven pressure-rated materials and certified fabrication methods to guarantee containment integrity under all operating conditions.

2. Pressure Rating and Target Operating Ranges

Hyperbaric chambers are defined by the pressure ranges they can achieve, typically measured in atmospheres absolute (ATA). The target pressure is determined by the chamber’s intended use. Mild hyperbaric chambers (often soft-shell designs for wellness) operate around 1.3 ATA (approximately 4 psi above atmospheric), which is the maximum allowed in the U.S. without medical device approval. These provide a modest increase in oxygen uptake (breathing air at 1.3 ATA yields ~26% O₂ intake vs 21% at sea level), and are mainly used for wellness or altitude sickness but not for treating serious medical conditions. Medical-grade chambers (hard-shell) typically operate at 2.0 ATA to 3.0 ATA for therapeutic HBOT. Most clinically proven protocols require at least 2.0 ATA to significantly increase tissue oxygenation. For example, the Undersea and Hyperbaric Medical Society (UHMS) approved indications generally call for ≥2 ATA pressure. Some acute conditions like gas embolism or carbon monoxide poisoning are treated at 2.8 ATA or higher, and Navy dive tables for decompression sickness can go up to 2.8–6.0 ATA in spec. However, pressures beyond about 3 ATA yield diminishing returns and increased risk of oxygen toxicity and other adverse effects. Thus, chambers intended for human therapy are usually designed for a maximum of ~3.0 ATA (around 44 psi) with appropriate safety margins. Research and experimental chambers (e.g. for diving research or engineering tests) might be built for higher pressures (5+ ATA) or custom profiles, but these require extremely robust construction. In all cases, the chamber and its components must be rated for the maximum pressure plus a safety factor (often 1.5 or more times the working pressure). Precise pressure control across the range is also essential to avoid barotrauma: typically compression and decompression rates are limited to a few psi per minute in operational protocols. In summary, the design must accommodate the specific pressure range needed – from mild 1.3 ATA units to high-pressure medical/research chambers – and include a generous safety buffer above the intended working pressure.

3. Hard-Shell vs. Soft-Shell Chamber Designs

Chamber design type is a fundamental consideration, as hard-shell and soft-shell chambers differ greatly in capabilities and use cases. Hard-shell chambers have rigid pressure hulls (usually steel or aluminum with acrylic windows) and can reach higher pressures (≥2.0 ATA) for true hyperbaric oxygen therapy. They are durable, long-lived structures built to pressure vessel codes, and most hospital/clinical chambers are hard-shell units. Soft-shell chambers have flexible walls made of tough fabric material and are inflated with air; they are limited to lower “mild” pressures (generally not exceeding 1.3 ATA by law). Soft chambers are valued for their portability and lower cost, making them popular for home or small clinic use in wellness contexts. However, they do not provide the same oxygen therapy benefit as high-pressure chambers. In fact, U.S. regulations stipulate that inflatable bag chambers are only authorized for treating altitude sickness – they are not FDA-approved for medical HBOT indications like wound healing or carbon monoxide poisoning. Additionally, soft chambers are prohibited from using pure oxygen supply (it is illegal “tampering” to pipe 100% O₂ into a soft chamber) due to fire risk and the device’s regulatory classification. By contrast, hard-shell chambers can safely use pure oxygen (with proper controls) and are cleared for medical treatments. The choice between hard vs. soft design impacts every other aspect: pressure capability, oxygen delivery method, regulatory requirements, and patient outcomes. Table 1 summarizes the key differences between soft-shell and hard-shell chambers.

4. Monoplace vs. Multiplace Chamber Configuration

Occupancy configuration is another major design decision. A monoplace chamber is built for a single occupant (one patient at a time), whereas a multiplace chamber accommodates multiple people simultaneously (e.g. 2–6 patients, and possibly a medical attendant inside). Monoplace chambers are often cylindrical tubes roughly 2.5–3 feet in diameter and about 7–9 feet long – just enough for one person lying down on a gurney that slides in on tracks. These are commonly used in hospitals for individual treatments. Monoplace chambers are usually pressurized with pure oxygen, essentially filling the entire chamber with 100% O₂ at the desired pressure. The patient breathes directly the high-pressure oxygen (often wearing a cotton garment to avoid static) and no mask is needed. Because the whole environment is oxygen-rich, nothing else (no electronics, no metal tools, etc.) can be brought inside except the patient and approved materials, to minimize fire risk.

Multiplace chambers, on the other hand, are larger steel rooms or cylinders that can treat several patients at once together. A typical multiplace chamber might be the size of a small room (e.g. 10 feet long and 8 feet wide), often with bench seating or gurney space for 2–6 patients. These chambers are pressurized with compressed air (normal breathing air), not pure oxygen, so the internal atmosphere is safer (nitrogen/oxygen mix) and allows intercommunication among occupants. Patients inside a multiplace breathe 100% oxygen via masks, hoods, or endotracheal tubes as needed, receiving the same therapeutic O₂ dose as a monoplace, but the chamber atmosphere remains only about 21% oxygen (or slightly higher). This greatly reduces fire hazards – multiplace units even incorporate fire suppression systems inside due to the presence of some oxygen equipment, though the overall fire risk is lower than in monoplace chambers. Another benefit of multiplace design is that a medical staff member can accompany patients inside (when large enough), providing real-time care or monitoring in critical cases. For example, in critical care HBOT, a nurse or technician may be inside the chamber with the patients, something not possible in a monoplace.

The choice of mono vs. multiplace impacts design requirements: multiplace chambers are much larger and built of thick steel, with multiple viewports and often an air-lock entry (a small vestibule that can be pressurized/depressurized independently to allow people to enter/exit without decompressing the whole chamber). They require high-capacity compressors and complex gas systems to supply several people. Monoplace chambers are more compact, often built with a large transparent acrylic cylinder for visibility, and have simpler operation (one patient, one set of controls). Both types must have pressure gauges and intercom communications so that the operator (who remains outside) can monitor and talk to the occupants. Ultimately, a facility might choose a multiplace chamber if treating many patients or if attendant-access is needed (e.g. treating young children or critical ICU patients under pressure), whereas monoplace units are efficient for standard outpatient therapies one patient at a time. Both configurations must meet the same safety standards and are classified by NFPA as Class A (multiplace, human occupancy multiple) vs Class B (monoplace, human single occupancy) chambers. There are also Class C chambers (animal use only) which are generally monoplace designs intended for veterinary patients (see consideration 18).

5. Gas Supply and Oxygen Input Systems

The choice of gas supply is central to hyperbaric chamber design. Chambers can be pressurized with either compressed air or oxygen, and pure oxygen can be delivered to the occupant via masks, hoods, or directly filling the chamber. Each approach requires specific equipment:

• Compressed Air Pressurization: Multiplace chambers and many soft chambers use air compressors to raise the internal pressure. This requires a reliable compressor system capable of providing high-pressure air (often 6–8 ATA output in multi-stage compressors, with regulators to control chamber pressure). The air must be clean, dry, and breathable – typically meeting medical breathing air standards (filtered to remove oil, carbon monoxide, and particulates). High-capacity storage tanks or cascade systems may be used to supply air quickly for large multi-patient chambers. Continuous ventilation flow is often needed (Environmental Control) which means the compressor must deliver a constant flow of fresh air. Soft-shell chambers usually include a small oil-free compressor (often ~0.5–1.0 HP) that provides airflow to both inflate the chamber and continually ventilate it; these are simpler but limited to low pressure.

• Oxygen Supply (Medical O₂): For monoplace chambers (or any scenario where the patient will breathe 100% oxygen), a medical-grade oxygen supply is required. This can come from pressurized O₂ cylinders, liquid oxygen (LOX) storage with a vaporizer, or an oxygen concentrator. Oxygen concentrators (PSA systems) are sometimes used for mild chambers or home units, but they have limited flow (often 5–10 L/min) and ~95% O₂ purity. High-pressure O₂ cylinders or hospital O₂ pipelines are more typical for true HBOT, delivering pure oxygen at regulated pressure and flow. The piping and valves must be rated for oxygen service – made of copper/brass or stainless steel, cleaned of any grease (to prevent fire in 100% O₂), and fitted with flash-back arrestors or check valves as needed. In multiplace chambers, each patient station will have a built-in breathing system (BIBS) which connects to an O₂ supply line and an exhaust line (to carry away exhaled oxygen out of the chamber). Monoplace chambers have a simple inlet valve from the O₂ source to flood the chamber, and an outlet valve to vent excess gas.

• Pressure and Flow Regulation: The gas input system must include regulators to prevent over-pressurization. For example, oxygen supply lines should have pressure regulators to step down cylinder pressures (which can be 2000+ psi) to the working pressure of the chamber (e.g. 15–45 psi range). Automatic flow controllers or manual needle valves are used to control the rate of pressurization – allowing operators to pressurize the chamber at a safe rate (often 1–3 psi per minute). As noted in a recent safety review, the medical gas system must be able to “provide pure oxygen at the correct flow rates” and “regulate the pressure to prevent overpressurization." Redundant safety regulators and pressure relief valves (Safety Mechanisms) are installed to ensure no single failure can over-pressurize the chamber.

• Ventilation and Exhaust: The gas system also needs a way to vent gas from the chamber. This is used both for depressurization (bringing the chamber back to 1 ATA) and for continuous ventilation during therapy. In a pure O₂ monoplace chamber, the chamber continuously vents excess oxygen to keep the internal temperature comfortable and remove CO₂ – this vented oxygen must be piped to a safe outside location to avoid oxygen buildup in the facility. In multiplace chambers, each patient’s exhaled oxygen (from masks/hoods) is scavenged by a vacuum exhaust and vented out to prevent the chamber air from becoming O₂-enriched. Thus, the design includes exhaust piping, pressure let-down orifices, and possibly mufflers (to reduce noise of venting gas).

In summary, the gas supply design should detail whether the chamber uses air or oxygen pressurization, size the compressor or O₂ source for the chamber volume, and include all necessary regulators, filters, piping, and alarms. All components must be suitable for high-pressure oxygen service. A properly installed system will deliver oxygen safely and reliably, as emphasized by standards like NFPA 99 and ASME PVHO which address medical gas system design. Using certified medical gas installers and following codes helps ensure there are no leaks or incorrect connections in this critical life-support system.

6. Pressure Control, Relief Valves and Emergency Venting

Safe pressure management is critical. The chamber must have mechanisms to control and relieve pressure to protect both the occupants and the structure:

• Primary Pressure Controls: The operator (or an automatic control system) should be able to precisely control pressurization and depressurization rates. This is often achieved with manual needle valves or computerized valves that throttle the incoming gas and outgoing vent. Modern chambers increasingly use automated digital pressure regulators to avoid human error, which can keep pressure constant and adjust rates smoothly. The control panel will typically include a pressure set-point control and a valve for emergency exhaust.

• Over-Pressure Relief Valves: Every pressure vessel needs one or more spring-loaded safety relief valves set to open if internal pressure exceeds the design limit. These are usually calibrated slightly above the maximum operating pressure (for example, if max working pressure is 3.0 ATA, a relief might open at ~3.3 ATA). The relief valve prevents catastrophic failure of the chamber by venting gas if the pressure regulator or control valves malfunction. It must be sized to vent gas as fast as the system could possibly pressurize. Over-pressurization leading to structural failure is a known hazard – a stuck valve or operator error could otherwise cause a dangerous pressure rise. Thus, redundant relief devices (one on the chamber, and sometimes one on the supply line) are good practice. These valves should exhaust to a safe area (especially if venting oxygen).

• Emergency Dump / Rapid Decompression: In certain emergencies – notably a fire inside the chamber – the protocol may call for rapid decompression to 1 ATA. Chambers often have an emergency vent valve (sometimes a large diameter ball valve or “dump” valve) that can be fully opened to quickly let out pressure. While a sudden decompression is risky (can cause barotrauma to ears/lungs if done too fast), in a fire scenario the priority is to remove the pressurized oxygen that is feeding the fire. NFPA 99 requires that a chamber be able to rapidly vent in the event of fire. For example, monoplace chambers can be depressurized in well under 1 minute in an emergency, sacrificing the treatment to save the patient’s life. The emergency vent control is usually accessible both to the operator and sometimes to the patient inside (a manual release knob), though patient-initiated vents are typically guarded to prevent accidental use.

• Pressure Gauges and Indicators: Although a monitoring topic, it’s worth noting every chamber has at least one analog pressure gauge (bourdon tube type or digital) that continuously displays internal pressure in ATA or PSI. Often one gauge is inside for occupants and one outside for the operator, cross-checking accuracy. These help the operator manually regulate valves to maintain the desired pressure and see any anomalies.

All these mechanisms must be regularly tested and calibrated. They ensure that even if the main control system fails, the chamber will not exceed safe pressure. Past accidents have shown that not having proper reliefs or functioning controls can lead to explosions or implosions of chambers. Thus, this consideration is tied closely to the structural design and regulatory compliance (ASME PVHO-1 requires specific relief device criteria for pressure vessels). In designing a chamber, one must incorporate multiple layers of pressure protection: accurate controls, mechanical relief valves, and clearly visible pressure readouts.

7. Fire Safety and Suppression Systems

Fire is one of the gravest dangers in hyperbaric environments, especially when high concentrations of oxygen are present. The chamber design must minimize ignition risks and include provisions to detect and suppress fire quickly:

• Material Selection and Configuration: The interior of the chamber should be constructed and furnished with fire-retardant materials. This includes using metal or flame-resistant coatings on surfaces, and avoiding any flammable textiles or plastics. For example, NFPA 99 specifies that internal finishes in Class A chambers meet Class A flame spread ratings. Patients and staff are typically required to wear 100% cotton or similarly non-static, non-synthetic garments to avoid static sparks and melting fabrics. No ignition sources (open flames, sparking equipment) are allowed inside. Electronic devices are either forbidden or specially designed to be intrinsically safe in high O₂. The chamber should also be electrically grounded (bonded) to dissipate any static charge.

• Oxygen Concentration Control: Because oxygen-rich atmospheres drastically increase flammability, multiplace chambers keep ambient O₂ levels at or near normal (21%). If a monoplace is filled with 100% O₂, the risk of fire is extremely high – in such cases even a small spark can cause a flash fire that spreads in the pure oxygen. Therefore, hyperbaric chambers must control oxygen levels and limit any excess O₂. Ventilation (discussed later) is used to keep ambient O₂ in a safe range (often <23-25% in multi-place). Gas monitors also trigger alarms if O₂ rises too high. By keeping oxygen only where needed (in masks/hoods for patients, rather than flooding the whole chamber), multiplace designs inherently reduce fire hazard.

• Fire Detection: Some large chambers include smoke detectors or temperature sensors in the chamber to alert operators to a fire. In practice, due to the confined space, any fire will be immediately obvious to those inside (smoke, flame, heat). Nonetheless, automatic detection can trigger emergency responses (e.g. sound an alarm, cut off oxygen supply).

• Fire Suppression: Sprinkler or water mist systems are often installed inside multiplace chambers. NFPA 99 requires that the room housing the chamber have an automatic sprinkler system, and many Class A chambers include an internal fire suppression system as well. Water mist nozzles can rapidly douse a fire without the flood damage of a full sprinkler. Portable fire extinguishers (water-filled, not CO₂ or dry chemical in oxygen environments) can also be kept inside if an attendant is present. In a monoplace oxygen chamber, internal suppression is less common (there’s no one inside to operate an extinguisher, and discharging anything in a 100% O₂ environment is problematic). Instead, the protocol in event of fire is to immediately depressurize and flood the chamber with air to smother the fire. Operators are trained to hit the emergency vent and halt oxygen flow at the first sign of combustion.

• Pressure Vessel Resistance to Fire: The chamber structure itself should withstand the thermal stress of a fire long enough to get occupants out. This means using metals that don’t weaken excessively at high temperature. Acrylic viewports are a vulnerability – they can ignite or melt in high O₂ fire. PVHO standards address this by requiring certain thickness and coatings, but ultimately a severe fire can compromise an acrylic window. That underscores why prevention and rapid suppression are key.

• External Room Safety: The facility around the chamber must accommodate fire safety too. NFPA 99 classifies hyperbaric rooms based on chamber type: e.g., a room with Class A (multiplace) chambers must be enclosed in a 2-hour fire-rated room to contain a fire. The room will have sprinklers and also an exhaust to outside to vent any oxygen that leaks or is dumped. Electrical outlets in the room may need to be explosion-proof if oxygen could accumulate. Additionally, signage and training are required: no flames, spark potential devices, or flammable liquids near the chamber.

Fire safety is built into the design through materials, atmosphere control, and suppression systems. Every aspect, from forbidding certain items (like petroleum-based products or electronics without approval) to including emergency deluge systems, is aimed at preventing the kind of tragic accidents that have occurred historically when these measures were absent. As one safety review noted, compliance with NFPA 99 and oxygen handling standards is absolutely critical – ignoring these has led to devastating accidents in the past.

8. Regulatory Requirements and Standards Compliance

Hyperbaric chambers straddle the domains of medical devices, pressure vessels, and specialized facilities – hence, they are subject to numerous regulations and standards. Ensuring compliance is a top consideration during design and construction:

• Medical Device Regulations (FDA & CE): In the United States, a hyperbaric chamber intended to treat medical conditions is considered a Class II medical device. Manufacturers must obtain FDA 510(k) clearance, demonstrating substantial safety/effectiveness for intended uses. The FDA will expect compliance with design standards like ASME PVHO and certain UL electrical standards, as well as labeling and instructions for use. Soft chambers marketed for general wellness often avoid medical claims to bypass FDA regulation, but legally they are only cleared for treating altitude sickness. In the EU, chambers fall under the Medical Devices Regulation (MDR) for medical use, requiring CE marking. European standards such as EN 14931:2006 provide specific hyperbaric chamber requirements for performance and safety (including ventilation, contaminant limits, etc.). Compliance with the Pressure Equipment Directive (PED) is also necessary for pressure vessels in Europe.

• Pressure Vessel Codes: As mentioned, the ASME PVHO-1 standard (“Safety Standard for Pressure Vessels for Human Occupancy”) is the primary code in the U.S. for chamber structural design. It covers material selection, design stresses, fabrication processes, testing (e.g. hydrostatic tests), and required appurtenances (viewports, fittings) for any vessel that humans enter under pressure. Many jurisdictions require an authorized inspection and stamping of the chamber pressure vessel (similar to a boiler inspection) to certify it meets ASME code. In some cases, ASME Section VIII, Div.1 (unfired pressure vessels) is used in conjunction with PVHO-1. The HVM veterinary chambers, for example, note that they are manufactured in accordance with ASME Boiler & Pressure Vessel Code Section VIII-1. For acrylic windowed chambers, PVHO-2 gives guidelines on in-service inspection and replacement of viewports (since acrylic has a limited lifespan under pressure cycles).

• Fire and Electrical Codes (NFPA 99): NFPA 99 (Health Care Facilities Code) Chapter 14 specifically addresses Hyperbaric Facilities. It classifies chambers as Class A/B/C and lays out requirements for construction, fire protection, electrical safety, and operations. Key points include: Class A (multi) chambers must be in a dedicated fire-rated room, only hyperbaric usage in that room; electrical installations must consider the enriched oxygen environment (use Class I, Division 2 rated equipment if >23.5% O₂); ventilation minimums (3 CFM per person not on BIBS); and emergency preparedness. NFPA 99 is often legally mandated by authorities (e.g. Centers for Medicare/Medicaid in the U.S. require compliance). Similarly, the National Fire Protection Association code 53 (older NFPA 56A/56D) and NFPA 101 Life Safety Code may have relevant sections.

• Other Standards and Guidelines: The Undersea and Hyperbaric Medical Society (UHMS) provides industry guidelines and facility accreditation standards for hyperbaric centers. Following UHMS best practices (for chamber design, staffing, and safety programs) is recommended and often required for insurance or hospital credentialing. OSHA guidelines apply if staff are exposed to pressurized environments or if the chamber is used in industrial settings (e.g. OSHA limits on compression rates for pressurized work). In addition, Compressed Gas Association (CGA) standards guide medical gas storage and pipeline delivery in hospitals, which would cover the oxygen supply system feeding the chamber. For veterinary chambers, there may be animal welfare regulations and recommendations by veterinary organizations for safe HBOT use in animals (ensuring monitoring, etc., though these are not as codified as human standards).

• Labeling and Documentation: A compliant chamber will have proper labels (serial number, max pressure, manufacturer, test dates) and a comprehensive technical manual. Maintenance logs and periodic inspection (required by PVHO-2 for viewports, for instance) must be maintained to stay within regulatory compliance.

In short, designing to code is not optional, it’s a fundamental consideration. Non-compliance can have legal consequences and, more importantly, safety consequences. Builders should engage experts and certified professionals to ensure every aspect of the chamber (from pressure vessel to fire systems to gas plumbing) meets the applicable standards and passes any required inspections.

9. Environmental Control (CO₂ Scrubbing, Ventilation, Climate Conditioning)

Inside a sealed hyperbaric chamber, the atmospheric environment must be carefully controlled for occupant comfort and safety. Key factors include carbon dioxide (CO₂) levels, temperature, and humidity:

• CO₂ Removal: Humans (and animals) exhale CO₂, which can accumulate in an enclosed chamber, leading to dangerous hypercapnia (CO₂ buildup). Even at normal pressure, CO₂ above ~1–2% can cause headache, drowsiness, and >5% can be very harmful. Under pressure, the partial pressure of CO₂ is higher for the same percentage, worsening its physiological impact. Therefore, chambers must have a method to prevent CO₂ accumulation. The primary method is ventilation with fresh gas (called Hyperbaric Chamber Ventilation, HCV). Continuous or periodic flow of new air/O₂ into the chamber flushes out exhaled CO₂. Standards exist: for example, European standard suggests a minimum of 30 liters per minute of fresh air per occupant for CO₂ control. NFPA 99 (2021) requires about 3 actual cubic feet per minute (≈85 L/min) of ventilation per person not on a mask. The U.S. Navy diving manual recommends 2 ACFM (~57 L/min) per resting occupant to keep CO₂ below 1.5% SEV (surface equivalent value). Practically, multiplace chambers achieve this by constantly bleeding in air from compressors and venting the stale air out. In monoplace chambers pressurized with O₂, a continuous flow of oxygen through the chamber (often on the order of 100–150 L/min) is provided, which carries away CO₂ through the vent. Some chambers also use CO₂ scrubbers with chemical absorbent (soda lime) especially if ventilation flow is limited – similar to a rebreather system, the scrubber unit pumps chamber air through soda lime canisters to chemically remove CO₂. CO₂ scrubbing may be needed in research chambers or when very low flow rates are used. In any case, monitoring CO₂ levels (see Monitoring section) is important to verify that CO₂ remains in safe range (often target <0.5% or < 5 mmHg CO₂ partial pressure). Adequate ventilation design also helps remove any exhaled contaminants or odors and prevents pockets of CO₂ from forming.

• Temperature Control: Compressing gas heats it (per gas laws), so during the compression phase the chamber air can warm significantly. Likewise, expansion during decompression causes cooling. Additionally, occupants and electronic equipment generate heat, and high-pressure oxygen can increase metabolic rates slightly. Without control, chamber temperature could become uncomfortably hot during long treatments or very cool when depressurizing. Many chambers include air conditioning or heat exchange systems. A multiplace chamber might have a dedicated HVAC unit that cools the incoming air (or a water-cooled heat exchanger loop around the chamber). Some systems pre-cool the ventilation air or use an internal fan coil that circulates chamber air through a cooler. Monoplace chambers often rely on adjusting oxygen flow temperature – e.g. using a chilled water jacket around the incoming oxygen supply line, or simply controlling room temperature since the chamber will equalize toward ambient after the initial heat of compression. NFPA 99 notes that chamber facility rooms should be kept around 80 °F (27 °C) and at least 50% humidity to help with temperature control. Patient comfort is usually maintained at around 72–78 °F inside the chamber. If the chamber runs a bit warm due to compression, operators may cool it by ventilating with cooler air or by shortening compression time.

• Humidity Control: Humidity tends to rise in a closed chamber from people exhaling moisture and from any influx of humid air. High humidity can cause condensation on viewports, discomfort, and even affect electronics or increase risk of static discharge if too low. Ideally, keep relative humidity moderate (40–60%). Some chamber ventilation systems include dehumidifiers or moisture separators. For example, as part of an environmental control unit, the incoming air may be passed through a condenser coil to drop out moisture. Conversely, extremely dry air (low humidity) can irritate occupants’ airways and increase static, so in some climates a bit of humidity is added. Most often, controlling humidity is achieved by controlling the ventilation rate and using air at comfortable humidity. Chamber operators monitor it and adjust. NFPA 99 suggests maintaining chamber room humidity above 50% to avoid static issues, which indirectly helps inside. In long treatments (>2 hours), moisture can visibly condense; some chambers have drip pans or drains for that.

• Odor and Air Quality: The environmental control also covers removing odors (for example, if treating burn patients or infections, there may be unpleasant smells) by ventilation. Any toxic outgassing from materials (hopefully none if proper materials are used) should be vented. Using high-purity gases and avoiding pollutants is crucial – intake air should come from a clean source (outdoor away from engines). Some research chambers that house animals also integrate scrubbers for ammonia or additional filtration to handle animal waste odors.

The chamber should be designed as a life-support capsule with full climate control: providing fresh air to breathe (or sufficient O₂ flow), removing CO₂ and excess oxygen, maintaining a comfortable temperature, and avoiding condensation. Calculations for required ventilation rates per occupant are performed, and systems (blowers, fans, scrubbers, HVAC) are sized accordingly. An effective environmental control design is evident when patients report the chamber is comfortable and easy to breathe in for the entire session, without headaches or overheating – a result of proper CO₂ and climate management.

10. Monitoring and Instrumentation Systems

A comprehensive suite of monitoring devices is essential to oversee chamber conditions and patient safety in real time. The chamber should be equipped with instruments for all critical parameters, often with redundant readouts for the operator and the occupant:

• Pressure Gauges: As mentioned, an accurate pressure indicator (analog gauge and/or digital display) is mandatory. Most chambers have a large bourdon-tube gauge calibrated in ATA, feet of seawater, or psi, visible to the operator. A secondary gauge inside the chamber allows the person (or internal attendant) to verify pressure. Digital pressure transducers may feed a controller and provide precise readings to 0.01 ATA. Regular calibration against a standard is needed to ensure accuracy, as treatment profiles (and safety limits) depend on knowing the true pressure.

• Oxygen Analyzers: Monitoring the oxygen percentage inside the chamber is crucial, especially for multiplace chambers where oxygen is introduced via masks and can leak. An oxygen sensor (electrochemical or galvanic fuel cell type) continuously measures ambient O₂. The system typically triggers an alarm if O₂ goes above a threshold (e.g. >23% which indicates an oxygen-enriched atmosphere that heightens fire risk. In a monoplace chamber that is intentionally 100% O₂, the monitoring is more about ensuring the patient’s oxygen is adequate and knowing when to stop oxygen if a break is needed to avoid toxicity (some monoplace protocols have “air breaks” where they switch to air for a few minutes to reduce oxygen toxicity risk). Nonetheless, O₂ monitoring is used to verify the chamber isn’t losing oxygen (in case of a leak) and that the cycle timing is correct.

• Carbon Dioxide Monitors: A CO₂ monitor should be installed to track CO₂ levels in the chamber air. This is often an infrared sensor that can operate at pressure. It provides an alert if CO₂ rises above safe limits (e.g. 1.0% or 10,000 ppm in normal operating conditions, and certainly if >2–3%). This helps verify that ventilation is sufficient and can warn of any failure in the scrubber or vent system. Modern hyperbaric environmental monitors combine O₂ and CO₂ sensors with digital displays.

• Carbon Monoxide (CO) and Other Gases: If compressed air is used, CO monitoring is recommended on the intake, because a compressor pulling air from a facility could ingest carbon monoxide (from vehicle exhaust, for example) and poison occupants. Thus, many systems have a CO detector to ensure levels stay below a few ppm. Likewise, humidity sensors and temperature sensors might be part of an integrated unit. Some advanced monitors measure a range of variables (O₂, CO₂, CO, temperature, humidity, and pressure) and log the data.

• Patient Vital Sign Monitoring: While not part of the chamber construction per se, considering how to monitor the patient’s condition is important. In multiplace chambers, attendants can use standard vital monitors (or special pressure-compatible models) to track blood oxygen (pulse oximeters), heart rate, blood pressure, etc. In monoplace chambers, any electronic monitor going inside must be approved for hyperbaric use (battery-operated and plastic cased to avoid sparks). Often, patients are simply clinically monitored (via intercom: “are you okay?”, or viewing through the acrylic). Newer monoplace designs sometimes include ports for medical lines or cables – for instance, a penetrator for ECG leads or an internal transducer that can transmit data through the chamber wall. This must be planned in design: small sealed feed-through connectors can be installed for running IV lines or wires without compromising pressure integrity.

• Alarms and Data Logging: All monitoring systems usually tie into audible/visual alarms that alert if a parameter goes out of range (high oxygen, high CO₂, high/low pressure, etc.). The control system might automatically take action (e.g., stop oxygen flow if oxygen % too high). Logging of treatment profiles (pressure over time, O₂%, etc.) is valuable for both safety and regulatory record-keeping. Many chambers now have computerized monitoring that records each session’s pressure profile and environmental readings, which can be reviewed later.

• Communications (Intercom) Monitoring: While covered more in the UI section, note that an intercom is effectively a monitoring tool so that operators can hear and talk to those inside – if a patient indicates distress or if an attendant reports an issue, the operator needs that feedback immediately.

A robust monitoring setup acts as the chamber’s “senses and brain,” ensuring the environment stays within safe limits. Installing redundant sensors (e.g., two O₂ sensors for confirmation) and performing regular sensor calibration are also part of this consideration. A properly instrumented chamber will have multiple dials and digital readouts on the control console, and perhaps an external panel or software interface showing all current levels at a glance. This gives the hyperbaric technician confidence that conditions are correct – and if anything drifts, they will know right away and can correct it.

11. Control Systems and User Interface

The user interface (UI) and control system determines how operators and possibly occupants interact with the chamber. A well-designed control system enhances safety by making operation straightforward and providing fail-safes:

• Operator Control Console: Most hyperbaric chambers have an external control panel where the operator sets the pressure and monitors the chamber. This typically includes valves (for air/O₂ inlet and exhaust), pressure gauges, and environmental readouts as discussed. In advanced systems, a PLC (Programmable Logic Controller) or computer is integrated to automate sequences. For example, an operator might select a treatment profile and the system will automatically pressurize to 2.0 ATA over 10 minutes, hold for 90 minutes, then decompress over 10 minutes. Automation can improve consistency and reduce operator workload. Even so, manual controls are usually retained as a backup or for fine-tuning. The console UI should be clearly labeled and logically arranged (e.g., grouping gauges near their corresponding valves, using color-coding for oxygen lines vs air lines, etc.).

• Inside Controls: In monoplace chambers, there is often an internal emergency release knob or valve that the patient can turn to depressurize in an absolute emergency (like a fire or if the operator outside is incapacitated). These are usually guarded to prevent accidental use. Some monoplace units also have an internal “call” button or switch that activates an external alarm to get the operator’s attention. Soft chambers typically have a means for the user to start or stop inflation (like an internal valve or just the ability to unzip from inside once depressurized). For multiplace chambers with an inside attendant, there will be a set of internal controls to regulate oxygen flow to masks, to communicate via intercom (push-to-talk handsets), and possibly to operate the fire suppression or emergency vents from inside as well.

• Communication Interface: Two-way communication is vital. Most chambers use an intercom system with microphones and speakers (or headsets) enabling the chamber occupants and the external operator to talk. This helps with equalization coaching (“clear your ears”), status checks, and emergency instructions. The UI often includes push-to-talk buttons on the console and inside the chamber. Additionally, many facilities set up a closed-circuit TV camera on the chamber viewing window so the operator can visually monitor the patient’s condition (especially if the patient is not visible directly due to chamber design or if they are lying down covered with a sheet). Some chambers even provide entertainment via internal speakers or a video screen to keep patients at ease during long treatments – the control system may route audio in, etc., though any such devices must be chamber-safe (often external and viewed through a window).

• Indicators and Feedback: The UI should provide clear feedback to the operator. For instance, indicator lights might show when valves are open or closed (in automated systems), an alarm light flashes if an emergency condition triggers (accompanied by sound). If multiple chambers are operated from one control station (common in clinics), the controls must be well segregated and labeled per chamber to avoid confusion.

• Ease of Use and Training: A thoughtfully designed control interface contributes to operator training effectiveness. If controls are overly complex or non-intuitive, the chance of error increases. Many modern hyperbaric consoles are designed with human factors in mind – large, easy-to-read analog gauges for the most critical parameter (pressure), touch-screen displays for less critical settings, and physical emergency stop valves that are easily reached. The goal is that an operator under stress (say, responding to a patient emergency) can quickly and correctly operate the chamber to decompress or change gas without fumbling. As noted in safety literature, having automated pressure controls and fail-safes significantly helps avoid errors that lead to incidents.

• Maintenance Mode / Diagnostics: The control system may also have diagnostic modes to test valves, calibrate sensors, etc. For example, an electronic control might do a leak test by pressurizing slightly and monitoring pressure decay. These features aid maintenance technicians and should be user-friendly as well.

In essence, the user interface links the human operators to the complex chamber environment. It should be reliable (with backup power, see next section), clear in presentation, and as automated as practical while still allowing manual override. Whether it’s a simple analog panel on a soft chamber or a computer-controlled multiplace chamber, the interface needs to facilitate safe operations through clarity and appropriate technology.

12. Electrical and Power Safety

Hyperbaric chambers involve electrical components (lighting, communication, instrumentation, sometimes heating/cooling systems), and when high oxygen levels are present, electrical safety becomes paramount to prevent sparks or overheating that could ignite a fire. Key considerations include:

• Use of Intrinsically Safe Electronics: Any electrical device used inside a chamber with elevated O₂ must be designed to not spark or overheat. This typically means using intrinsically safe or explosion-proof rated equipment. For example, interior chamber lights are often LED-based with sealed housings or fiber-optic lighting where the actual bulb is outside and light is piped in. Communications inside might use sound-powered phones or specially made intercoms that run on low-voltage and have no sparking contacts. Items like fans, if used internally, need brushless motors and spark arresting design. In 100% oxygen monoplace chambers, usually no powered electrical device is inside at all (except perhaps a simple buzzer or microphone with carefully isolated circuitry). Even patient monitoring leads must be specially designed (ferrous parts can spark if MRI used, but hyperbaric mainly cares about heat and spark – some avoid any batteries or use external transducers). The rule of thumb: any electrical circuits in oxygen-enriched atmospheres must be ignition-proof. This includes considering that at 2–3 ATA, even air (21% O₂) effectively has a higher oxygen partial pressure, making things more flammable than at sea level.

• External Electrical Safety: The chamber itself should be thoroughly grounded to earth. This prevents static build-up and also ensures any fault currents (from a shorted wire touching the chamber, for instance) go to ground rather than through a person. All electrical feed-through connectors on the chamber hull must maintain pressure seal and insulation. The facility’s electrical system may need to treat the chamber room as a “hazardous location” if oxygen could be released – for instance, NFPA 70 (NEC) might classify the area around vent outlets as Class I Div 2 hazardous (requiring sealed conduit, explosion-proof fixtures) since high oxygen could come out during venting.

• Lighting: Adequate illumination inside is needed so occupants feel comfortable and staff can observe them. Many monoplace chambers have an internal light that the patient can turn on/off or it’s on a timer. These are designed to run cool (LED or low-wattage DC bulbs) and are mounted behind protective covers. In multiplace chambers, light fixtures are typically recessed and have thick viewports or quartz windows, with the bulb outside the pressure boundary – so if a bulb bursts or arcs, it’s not in the oxygen-rich interior. As a design choice, using natural lighting via acrylic windows also helps (some chambers have large clear sections that let ambient room light in).

• Electrical Feed-Through and Isolation: Any electrical wiring that goes into the chamber (for sensors, intercom, etc.) passes through special penetrators that maintain the pressure seal. These connectors have to be robust and not become hot under load. Isolation barriers may be used so that internal circuits are low-energy. Also, often the entire chamber (if metal) acts as a Faraday cage, so radio signals cannot penetrate – thus any internal wireless devices won’t communicate out. Designers sometimes provide a coax feed-through for radio frequency if needed, or mount an antenna inside connected to an external jack (for example, some vet chambers use wireless cameras inside, which require a means to get signal out, often via a feed-through or by placing the camera right against an acrylic window).

• Electromagnetic Compatibility: In a hospital setting, chamber electronics should not interfere with other medical devices (and vice versa). For instance, the control system and monitors should be shielded against RF interference. This is usually handled by adherence to IEC medical device electrical safety standards.

A real-world cautionary tale: a single spark from a faulty electrical device or static discharge in a hyperbaric oxygen chamber can trigger a flash fire. Thus, extreme measures are justified – e.g. grounding every piece of metal, banning personal electronics (no cell phones or hearing aids unless cleared), and verifying low voltage circuits. During design, one should review all electrical components with a hazard analysis: Is this component necessary? Can it ignite in worst-case? If uncertain, replace it with a pneumatic or manual alternative. The NFPA hyperbaric standards and OSHA guidelines will often call out which electrical items are permitted and how to install them. By scrupulously following these, the risk of an electrical ignition can be mitigated.

13. Power Supply and Backup Systems

A reliable power supply with backups is important for hyperbaric facilities to ensure that critical systems remain operational throughout a treatment (and during any emergencies). Considerations include:

• Primary Electrical Supply: Chambers are usually powered by normal AC mains to run the control systems, air compressors, oxygen valves, lighting, etc. The electrical design should accommodate the current draw of compressors (which can be significant on startup), climate control units, and any vacuum pumps for BIBS exhaust. It’s wise to have a dedicated circuit or even a dedicated panel for the hyperbaric system to avoid overloads and allow easy shutoff in emergency. Proper surge protection and power conditioning might be needed for sensitive electronic controls.

• Uninterruptible Power Supply (UPS): Critical control components (like an automated control system or monitoring alarms) should be backed by a UPS or battery power. In the event of a building power outage, the chamber will not immediately lose pressure (it’s a sealed vessel), but you could lose lighting, communications, and the ability to control valves if they are electrically actuated. Therefore, backup power ensures that at minimum the intercom, internal lights, and monitoring remain on, and ideally the control valves too if automated. If the chamber is mid-treatment during a power loss, staff can manually operate valves (assuming the design allows manual override) to safely decompress the chamber – but doing so in darkness or without comms is hazardous. A UPS gives a window of time to restore power or get everyone out safely. Many hospital hyperbaric units are on the facility’s emergency generator circuits, so that power is restored within seconds of an outage. The design should thus include an automatic transfer switch to emergency power for the chamber systems.

• Pneumatic/Manual Backup Controls: Even aside from electrical backup, good design provides manual backups for any critical function. For example, if an electrically driven valve fails or loses power, there should be a manual by-pass valve to control pressure. Some chambers use entirely pneumatic controls (using air pressure to actuate valves) which inherently continue to work without electricity, albeit those often still need compressed air to function. The emergency exhaust dump is usually a mechanical valve that can be opened by hand.

• Life Support Backup: If the chamber relies on pressurized oxygen from a concentrator or liquid oxygen pump that needs power, a backup supply of oxygen (e.g., reserve cylinders with a manual switchover) is necessary in case of power failure to that system. Otherwise, a patient inside might deplete the oxygen and suffocate if no fresh supply is coming in. Similarly, if a chamber is full of 100% oxygen and power is lost, CO₂ could build up if no ventilation – so either the UPS should power a minimal ventilation or the protocol would be to end the treatment early. Designs should consider fail-safe modes – for instance, normally-open exhaust valves that vent the chamber if power is completely lost and no operator action (ensuring the patient isn’t trapped under pressure for long). However, failing open may not always be desirable (could be risky to drop pressure unattended), so it’s a decision for design and procedural mitigations.

• Alarms on Power Failure: There should be an audible alarm if power fails, to alert staff. In many cases, hyperbaric chambers are staffed constantly during treatment, so the staff will notice if lights go out. But if the facility runs soft chambers at home, for example, the user must be instructed to abort treatment if power goes out (since compressor stops). Including something like an emergency battery light inside a monoplace that kicks on if main power fails is a good safety addition to prevent panic in darkness.

• Compressed Air Reserve: On the pneumatic side, some facilities keep a compressed air reserve tank that can be used to vent or pressurize a chamber if the compressor stops. For example, to decompress a chamber that’s stuck, you might need to drive the pneumatic exhaust valves – having a tank of air can supply the pressure to operate those controls.

Redundancy in power and controls ensures that a hyperbaric chamber doesn’t become a liability during power outages or equipment failures. This is akin to life support systems in an ICU – you’d have battery backup for a ventilator, so similarly for a chamber. Considering worst-case scenarios (power grid failure, natural disaster) during design leads to features like UPS, generator hookup, and manual overrides that keep people safe in all conditions.

14. Accessibility and Ergonomics

Designing a chamber for accessible and ergonomic use means making it easy and safe for people (or animals) to enter, exit, and remain in the chamber comfortably:

• Entrance Design: Chambers can have hatches or doors of various shapes – end caps that swing open, cylindrical side doors, or in soft chambers a long zipper along the side. It’s critical that the opening be large enough to accommodate the intended user and any required equipment (stretchers, wheelchairs). For medical use, most monoplace chambers have a horizontal sliding gurney tray: the patient lies on a stretcher that then slides into the tube, locking in place. This allows relatively easy transfer of bed-bound patients. Multiplace chambers often have a pressure door with a clear opening size (for example, 28–36 inches wide) that can allow a wheelchair or rolling gurney to go in. Some even have level flooring so a hospital bed can be rolled in directly. The door design must seal air-tight (using O-ring gaskets) and typically has a dogging mechanism (clamps or bolts) to secure it closed. Ergonomically, the door should be operable by staff without excessive force, and ideally open from both inside and outside (for emergency egress – though obviously only when not pressurized or via a pressure lock).

• Physical Accessibility: If treating patients with disabilities or injuries, the chamber should accommodate them. Handrails or grab bars might be installed inside multiplace chambers so ambulatory patients or staff can steady themselves (especially as pressure changes can affect balance). Seats in multiplace units should be stable and have belts if needed to secure patients during compression (since the noise and vibration might startle some). For veterinary chambers, special considerations include having cages or harness points inside if needed to restrain an animal safely, and doors that open fully to allow an animal (even a large dog or a sedated large cat) to be placed inside easily. Some vet chambers are designed with horizontal sliding doors or end caps to allow loading of gurneys with animals.

• Internal Space and Layout: Comfort is a factor especially in long treatments (which can last 1.5 to 2 hours). The chamber’s internal diameter and length should allow the occupant to assume a natural resting position. Monoplace chambers are somewhat confining due to being a narrow tube; using clear acrylic helps reduce the feeling of claustrophobia by allowing a full view outside. Some newer monoplace designs have a rectangular cross-section to give a bit more elbow room. In multiplace chambers, high ceilings (at least enough to stand or kneel) and enough floor area to stretch legs are desirable. Hyperbaric chamber entries also often have a step or ladder – providing non-slip steps or a small lift for wheelchair users is an ergonomic consideration.

• Door Safety and Emergency Egress: An ergonomic design also accounts for quick exit after decompression. Doors should open inward (most chamber doors are designed to be pressure-assisted closed, meaning they seal tighter when pressurized and can only open when pressure inside equals outside). Upon decompression, it should be quick to unlatch and swing open. Some designs have an interlock to prevent opening under pressure (for safety). Consider the worst-case of an unconscious patient – can two staff easily remove the person from the chamber? This may dictate door size and height (for example, aligning the chamber bed height with standard stretcher height to slide a patient out smoothly).

• Ergonomic Controls and Viewing: From the operator’s perspective, the chamber should have viewports placed such that the operator can see the occupants (heads/faces at least) to monitor signs of distress. Many monoplace units have multiple porthole windows along the side for this reason. Controls on the outside should be at a comfortable height and spacing for the operator to reach and adjust without strain. The environment around the chamber should have enough space to walk and access all sides for maintenance or emergency.

• Noise and Vibration: Another ergonomic factor is noise level. Compressors and valves can be loud. Good design includes mufflers on exhaust valves and may place the air compressor in a separate room to reduce noise near the chamber. This is not only comfort but also reduces stress for patients (and animals). Vibration isolators can be used on the chamber base if needed (though typically not an issue for stationary units).

Overall, user-centered design of the chamber improves both safety and patient experience. A well-thought-out chamber allows patients to easily get in position, clinicians to assist them without awkward maneuvers, and provides an interior where one can remain for hours without severe discomfort. For example, a multiplace chamber may have padded seating, adjustable stools for an attendant, and perhaps a transparent section so patients don’t feel closed in. Good ergonomics lead to higher compliance (patients willing to undergo treatment regularly) and lower risk of accidents (like trips or falls during entry/exit).

15. Internal Amenities and Patient Comfort Features

Beyond just fitting people, the chamber should consider comfort and amenity features to make the hyperbaric experience tolerable, especially for medical patients who may be in pain or anxious:

• Seating and Positioning: In multiplace chambers, provide comfortable seating – padded benches or individual seats. If patients will be supine (lying down) on gurneys, ensure there are mattress pads. There may be a need for multi-level seating or fold-down jump seats to maximize space usage. Some chambers include a stretcher rack system allowing two levels of stretchers (for critical care patients) stacked safely. Chairs should be made of suitable materials (e.g. vinyl upholstery that is fire-retardant and easy to clean). For animal chambers, often the animal is placed on a soft mat or in a ventilated pet carrier that goes inside; the interior should accommodate those.

• Visibility and Windows: Psychological comfort is greatly improved by having windows. Clear acrylic monoplaces provide 360° visibility, which is ideal for reducing claustrophobia. Multiplace chambers typically have multiple viewports (e.g. one on each door, several along walls). Larger diameter windows or even full transparent sections are nice but must balance structural integrity (acrylic needs thickness and has depth limits). Some chambers include an internal mirror so a patient can see outside or see an attendant. Lighting also affects comfort – soft, even lighting is preferable to a single harsh lamp. Dimmable lights can help if a patient wants to rest or if doing a transcutaneous oxygen measurement that requires low light, for instance.

• Communication & Entertainment: As mentioned, a reliable intercom reassures patients they’re not isolated. Many facilities go further by providing music or video. For example, an external DVD player’s video can be displayed through a window using a small LCD monitor sealed behind a viewport. Or audio music can be piped in through transducers on the hull. If safe, patients might be allowed to bring a book or magazine (paper is generally allowed if not oily or a fire hazard). Some monoplace chambers have been equipped with tablet computers mounted externally on the acrylic for patients to watch through the wall (the tablet stays outside to avoid risk). These features can significantly alleviate boredom and anxiety during a 90+ minute session.

• Noise Reduction: Inside a pressurized chamber, there is often background noise from gas flow and vents (a constant hiss) and from the external compressors. Effort should be made to reduce noise – use acoustic dampening on compressor lines, ensure exhaust mufflers are installed. Keeping noise to a low hum means patients can relax or even sleep. If an environment is too noisy, it can cause stress or communication difficulties over the intercom.

• Temperature Comfort: Already covered in environmental control, but from a comfort perspective ensure the patient isn’t too hot or cold. Often patients wear light cotton scrubs or a gown; providing a blanket (100% cotton, hyperbaric-safe) is common in case they feel cold, and the blanket also must be approved for use (clean, no lint that could clog filters, etc.).

• Sanitation and Cleanliness: Chambers should be easy to clean between uses. Interior surfaces are usually smooth and painted with epoxy or powder-coat that can be wiped down. In medical settings, infection control is important, so designs that minimize seams or cracks where dirt can accumulate are better. Some multiplace have floor drains to clean up any spills or if someone gets sick. A clean environment is also more pleasant for patients. For veterinary chambers, cleaning is crucial since an animal might urinate/defecate; thus chambers often have removable floor pads and surfaces that can be disinfected. Convenient cleaning means a better experience for the next occupant as well.

• Capacity for Attendant in Multi-Place: Having a person (nurse/technician) inside can significantly improve patient comfort and safety. So in bigger chambers, providing a small lock/airlock for an attendant to enter/exit if needed, and designing the interior with enough room for someone to move around, is valuable. The attendant can give sips of water, adjust a patient’s position, or just provide reassurance by their presence.

In conclusion, while it’s a technical piece of equipment, a hyperbaric chamber’s design should not ignore the human factor – making the inside as pleasant and user-friendly as possible. A patient who is comfortable and relaxed will have a safer and more effective therapy session. Many of these comfort features also overlap with safety (e.g. reducing stress reduces the chance of panic, which could lead to an emergency abort). Therefore, investing in good interior design and amenities is an important consideration in chamber construction.

16. Communication Systems and Surveillance

Continuous communication between chamber occupants and the outside operator is vital for safety and effectiveness. The design must incorporate reliable comms and the ability to observe the chamber interior:

• Audio Intercom: As described earlier, virtually all clinical chambers have a two-way intercom system. This usually consists of a microphone and speaker inside the chamber and a corresponding set outside. The system should function both at atmospheric pressure and under high pressure (some microphone diaphragms need to be pressure-compensated). It’s often hard-wired, with push-to-talk buttons. In multiplace chambers, each occupant might have an aviation-style headset or there may be ambient microphones such that normal speech inside can be heard outside (when activated). The operator can use the intercom to give instructions (e.g. “we’re starting compression now, remember to equalize your ears”) and to monitor for any distress (listening for calls or sounds). Designing the intercom to be clear and sufficiently loud over any background noise is important. Backup communication means should also be considered – for instance, if the intercom fails, having a set of pre-arranged hand signals through the viewport or a whiteboard inside can help.

• Visual Monitoring: Direct line-of-sight observation is ideal – hence chambers have viewports. The control console is often positioned so the operator can see in. For multiplace chambers with multiple windows, CCTV cameras can supplement views (one camera might not capture all angles). For monoplace, the entire side is transparent so usually one can see the patient fully. If the chamber is large or used for experiments without a person inside, interior cameras can be mounted to watch equipment or animal subjects. Any camera used inside must be rated for pressure and either be passive (no electricity inside, perhaps a fiber optic camera) or if electric, it must be hyperbaric-safe (some manufacturers make explosion-proof cameras for chamber use). Alternatively, cameras can be outside looking through a viewport. In veterinary chambers, watching the animal’s behavior (panting, agitation, etc.) is crucial; many have an external camera peering in.

• Emergency Signals: Beyond voice comms, there could be alarm signals the chamber can send. For example, a big red button inside that a patient can press to sound an alarm outside if they can’t speak (perhaps due to an oxygen hood or a medical issue). Conversely, the operator might have a signal (like a light flash or buzzer) to alert the inside attendant to something (if noise prevents hearing voice). Simple methods like a buzzer or flashing light can be understood as “check on patient #3” or “prepare for decompression” if standardized.

• Instrumentation Feeds: In research contexts, communication might include data lines (to get readings from sensors inside). Modern designs can incorporate wireless data transmission through the chamber wall via ultrasonic or RF repeaters, or simply use wired feed-through connectors. The ability for external computers to read inside conditions (like an animal’s vital signs on a telemetry) can be seen as a form of communication system too.

• Coordination with Medical Systems: In a hospital, the chamber likely connects (figuratively) with other hospital systems. For example, if a patient in a chamber has a bedside monitor outside, the staff need to reconcile those. A patient call bell system may be integrated such that if a patient in the chamber hits a call button, it alerts on the hospital nurse call system as well. While not directly a chamber design feature, planning the communication flow in emergency scenarios is important – e.g. having a phone or radio at the operator’s station to call a code team if needed, etc.

• Training and Protocols for Comms: This is operational, but relevant to design: the communications equipment should be user-friendly and robust, so that minimal training is needed to use it and it doesn’t break down often. Ideally, it has battery backup (so intercom still works if power fails). Additionally, design in redundancy where possible – maybe two separate intercom circuits if one fails (some multipurpose systems have a primary and secondary sound-powered phone line).

Proper communication and surveillance design ensures that those inside the chamber are never truly isolated, the outside world is just a button-press away. Many incidents have been averted or mitigated because an attentive operator heard a patient say they smelled smoke, or saw a patient become unresponsive and took quick action. Therefore, communication systems are as critical as any life-support component in the chamber.

17. Operational Protocols, Staffing, and Training Requirements

Even the best-engineered chamber can be dangerous without trained operators and strict protocols. Therefore, a key consideration in design is how the chamber will be used and by whom, ensuring that it supports safe operation procedures:

• Standard Operating Procedures (SOPs): From the outset, design should align with known hyperbaric procedures. This includes compression rates, treatment table profiles, and emergency procedures. For instance, if the protocol for decompression sickness is a US Navy Table 6 (spending ~4.5 hours with staged decompression), the chamber and its systems must be able to sustain that (e.g., enough oxygen supply for multiple oxygen periods, CO₂ scrubbers for duration, etc.). Protocols for pre- and post-use should also be considered: e.g. an SOP to pre-check valves and oxygen levels before each treatment – the design can facilitate this by including test ports or system self-checks. The design can incorporate visual aids or labels that reflect the SOP (like markings on valves for “treatment”, “emergency”, etc.).

• Staff Training and Roles: A hyperbaric chamber typically requires a trained operator (technician) and in medical settings, a supervising physician (often a hyperbaric medicine doctor). The design should assume a certain level of training – for example, a fully manual analog chamber demands more skill and attentiveness from the operator, whereas a computerized system might allow a less experienced operator to manage safely (though training is still required). Human factors engineering is key: many accidents historically were due to operator error, so designs that are forgiving (cannot easily be set up wrong) and have interlocks to prevent dangerous actions are preferred. Training programs (like those by UHMS or NFPA) often specify that chamber operators must understand things like oxygen toxicity signs, fire suppression activation, etc. The design should thus provide clear indicators and logs that can be used in training and post-incident review.

• Emergency Drills and Preparedness: The chamber should be designed to enable the execution of emergency protocols. For example, if an operator must get an unconscious patient out, the chamber should be able to be opened quickly (once decompressed) and perhaps have features like a rescue litter or slide that helps remove the patient. Training drills (for fire, sudden illness, etc.) will reveal if design elements need improvement (like adding internal quick-release buckles on patient restraints so they can be freed fast). Some large chambers even include a built-in firefighter’s breathing apparatus so an inside attendant can don a mask and suppress a fire – this level of complexity requires significant training.

• Maintenance Training: Operational protocol also extends to how staff maintain the chamber. Preventive maintenance schedules (daily, monthly, yearly checks) should be established, and the design should allow these to be done without undue difficulty. For instance, daily protocol may include cleaning the chamber, lubricating door O-rings, testing comms and analyzing oxygen sensor calibration. The design can help by providing easy access panels to filters, modular components that can be swapped, and an intuitive arrangement where nothing critical is hidden from view.

• Documentation and Logs: The chamber should come with comprehensive documentation – operation manual, safety manual, maintenance manual. It should specify maximum allowable operating limits, compatible devices, and emergency steps. All of this supports proper staff training. Many facilities require operators to be certified or credentialed; the design should meet the expectations of those certification bodies (like having the required safety features that an operator-in-training learns about).

• Staffing Requirements: A multiplace chamber might require 2–3 staff (an operator, and an inside attendant or tender, plus a safety director oversight). Design features like an external control lock (so an operator doesn’t accidentally change something while a lock is in use by someone else) or the ability to monitor multiple compartments, are relevant. In some jurisdictions, a Safety Director is mandated to manage hyperbaric operations – this person will ensure protocols are followed and the chamber is maintained. They will also ensure drills are run regularly.

The chamber should be designed for the user, not just the patient – meaning the staff who operate it daily. A user-friendly, well-documented system with built-in safety prompts will facilitate creating a culture of safety and adherence to protocol. Conversely, a confusing or unforgiving design can lead to mistakes even by trained personnel. Thus, bridging the gap between engineering and practical operation is a critical part of the design process.

18. Maintenance, Inspection, and Longevity

Building a chamber is not a one-and-done effort – it requires a plan for ongoing maintenance and periodic inspection to ensure it remains safe throughout its service life. Key considerations:

• Routine Maintenance: Many components have to be serviced regularly. O-ring seals on doors need cleaning and greasing on a schedule (often daily or weekly). Air compressors require filter changes, oil changes (if not oil-free type), and condensate drainage. Oxygen concentrators (if used) have sieve beds that need replacement after so many hours. The design should make these tasks straightforward – e.g., door O-rings that are easy to remove and replace, filter housings that are accessible. Soft chambers might require checking for fabric wear or zipper alignment before each use. A maintenance checklist should be established by the manufacturer.

• Inspection and Testing: Pressure vessels should undergo periodic inspection. This can include visual inspection for cracks or corrosion, pressure testing (e.g. hydrostatic test) at certain intervals, and specific checks like measuring acrylic window thickness for crazing or clouding. ASME PVHO has guidelines such as doing a thorough visual inspection of acrylic viewports at least annually, and typically requiring acrylic window replacement after a certain number of years or pressure cycles (e.g. some manufacturers recommend ~10 years for windows). The chamber design should thus allow window replacement (bolted flanges etc.). Pressure gauges and sensors need calibration checks perhaps yearly. Relief valves might be bench-tested and recalibrated yearly too. If the chamber is built to code, these inspections are often mandated by local pressure vessel laws (some places treat PVHO similar to boilers with required recertification).

• Cleaning and O2 Compatibility: After each use (especially in medical/vet scenarios), the chamber interior should be cleaned. Using approved cleaning agents (non-residue, non-flammable) is important. For oxygen chambers, everything inside must remain O2-clean (no oils). Maintenance includes ensuring any new component introduced (like swapping a valve) is cleaned for oxygen service. Also, any contamination (like patient blood or fluids) needs prompt cleaning to prevent corrosion or infection risk. Some chambers use liners or removable mats to help with cleaning.

• Lifespan and Parts Replacement: Different components have different lifespans. For instance, soft chambers might only be certified for ~5–10 years of use or a certain number of pressurization cycles before the fabric or seams need overhaul. Hard chambers can last decades (there are chambers from the 1960s still in operation) but may need refitting of subsystems over time. It’s important to have spare parts availability: valves, sensors, etc. The design should prefer standard parts (where possible) that can be obtained and replaced, or if custom, the manufacturer should guarantee parts support for a long period. The electrical control system might become obsolete in, say, 15 years, so planning for upgrades or ensuring an interface to replace it is wise.

• Documentation and Logs: A maintenance log book (physical or digital) is typically kept, noting all inspections, repairs, and part changes. The design can facilitate this by including hour meters on equipment (like a compressor hour meter to know when service is due) or by internally tracking number of cycles. Some advanced systems log pressurization cycles count which helps plan maintenance (like “window has 500 cycles, inspect at 1000 cycles”).

• Regulatory Compliance Ongoing: Facilities might need to undergo periodic surveys (e.g. by hospital accreditation bodies or hyperbaric facility accreditation). The chamber should be maintained to original specs to pass these. That means if any modifications are made, they should be re-evaluated under the standards (for example, installing a new type of light would require checking it still meets NFPA requirements).

Building with maintenance in mind ultimately saves cost and ensures safety. As an example, using a steel chamber vs an acrylic tube in a vet setting was cited because steel chambers have an “unlimited life cycle” with maintenance, whereas acrylic tubes have a limited life and expensive overhaul. Designing for durability (corrosion-resistant materials, robust coatings) and easy servicing (modular components) will keep the chamber operational for many years. A well-maintained chamber can safely treat thousands of patients over decades; a poorly maintained one can become a hazard in a short time. Thus, maintenance considerations are intrinsically part of the design criteria.

19. Intended Population and Use-Case Specific Adaptations

Hyperbaric chambers can be used for different populations – humans (adults/children), animals, and for various applications (clinical therapy, experimental research, etc.). The design may need special adaptation depending on who/what will be inside:

• Human Patients (Clinical/Wellness): For general human use, the design focuses on patient comfort (as discussed) and medical needs. If the chamber will treat pediatric patients, one might include attachments for entertaining children (like an external viewport for playing a movie or having space for a parent to accompany in a multiplace). For critically ill humans (ICU patients), the chamber might need to accommodate a ventilator, IV pumps, or monitors alongside the patient – multiplace chambers can be outfitted as mini-ICUs with these devices (which must be hyperbaric-rated or placed in pressure-exchange enclosures). If targeting the personal home use market, the design might emphasize simplicity and safety features since the operator could be the end-user themselves (e.g., an easy way to self-exit a soft chamber, clear instructions, and automated controls to avoid user error).

• Veterinary/Animal Use: Animal chambers (Class C) have some unique needs. Animals cannot always communicate discomfort, so design margins might be more conservative (slower pressure changes to avoid barotrauma, etc.). Animals may panic in confined spaces: chambers for animals often reduce external stimuli – for instance, the HVM veterinary chamber uses steel (opaque) construction to “limit outside distractions, allowing the animal to rest”, in contrast to the clear acrylic common for human chambers. For small animals (dogs, cats), the chamber might include internal dividers or cages so multiple animals can be treated without interacting (some vet clinics treat multiple pets at once for efficiency, as long as they are calm or sedated). For large animals like horses, there are very large chambers (horse can walk in). Those require extremely robust construction and special flooring with traction (to prevent slipping of hooves). Notably, a fatal accident in a horse chamber occurred when a horse kicked and its metal shoe created a spark – now design solutions include requiring no metal shoes or covering them, and ensuring nothing in the chamber can spark from impact. Also, sedation systems might be integrated: e.g., a way to safely administer anesthesia or calming agents prior to pressurization.

Designing for animals also means designing for waste management: an animal might relieve itself; a built-in flush or easy clean floor is important. Additionally, monitoring animals may require CCTV and remote physiological monitors (since they can’t speak). Some vet chambers incorporate oxygen sensors on the animal (like a hood or tent) because animals may not tolerate masks; others simply pressurize the whole chamber with oxygen for simplicity (which as discussed raises fire risk, so careful control and grounding of any metal on the animal is required).

• Research and Experimental Use: If a chamber is built for research (e.g., studying hyperbaric effects on isolated tissues, or testing diving equipment), the design might include a lot of feed-through ports for instruments. Researchers may need to insert electrical leads, fiber optic cables, or fluid lines through the chamber wall. Thus, multiple spare penetrations with valves (for sampling gas or inserting small devices) can be provided. The internal layout could be racks or mounting points for experimental apparatus instead of seats. In some cases, research chambers are dual-use as hypobaric (altitude) and hyperbaric; those need vacuum capability and more complex pressure control ranges. If the research involves simulated dives with gas mixtures (like helium-oxygen, etc.), then gas integration ports for multiple gases and analysis equipment might be installed.

• Diversity of Users: Think also of user population specifics: e.g., if the chamber is for wellness/spa clients, the design may be more inviting and less “medical” looking, with nicer interior finish and perhaps aromatherapy compatibility (ensuring any scents used are O₂ safe). If for military or diver training use, durability and the ability to do frequent pressure cycles and rapid turnarounds might be key (heavy-duty valves that can handle repeated compressions daily).

• Class A/B/C Differences: As noted from NFPA, Class C (animal) chambers are not to have human occupancy. This implies design might not need to consider human comfort, but ironically it must consider human safety still (the humans operating it outside). NFPA still requires the same room safety for Class C as for Class A/B in many cases. One difference: perhaps life support requirements are different – no “life support gas” in an animal chamber would be Category 1 (since humans not in danger if gas fails, only animal), which might reduce redundancy requirements for gas supply slightly. Nonetheless, veterinary chamber manufacturers often build to similar standards for liability reasons.

There is no one-size-fits-all: a chamber optimized for wound care in diabetic adults will look different from one for treating dogs with smoke inhalation, or one for testing electronics under pressure. Identifying early who the end users (and beneficiaries) are allows incorporation of the needed features (be it extra ports for lab sensors or special accommodations for anxious pets). The regulatory environment may also change with population – e.g., FDA oversight for human medical, vs fewer regulations for purely research or animal use (though still under animal welfare laws). Ensuring the design meets the specific demands of the target use case is crucial for the chamber to be effective and safe.

20. Supporting Equipment and Facility Infrastructure

Lastly, building a hyperbaric chamber isn’t just about the chamber alone, it involves the supporting infrastructure and how the chamber will be integrated into a facility:

• Space and Location: The physical site must accommodate the chamber’s size and weight. Hard chambers are extremely heavy (multi-place steel chambers can weigh several tons). The floor must be able to support this concentrated load, possibly requiring structural reinforcement. The chamber room should have enough clearance around for maintenance access and emergency egress. NFPA 99 mandates the room for Class A or B chambers be exclusively for hyperbaric use (no unrelated storage) and have a 2-hour fire barrier if Class A. Adequate ceiling height is needed if the chamber is tall or if overhead cranes are used to install components.

• Ventilation of Room: The facility should have general room ventilation, especially if using oxygen. Oxygen vented from the chamber (during decompression or through BIBS exhaust) must be ducted outside or the room ventilation must be sufficient to keep ambient O₂ below 23.5%. Many chambers have a dedicated exhaust fan triggered when venting to scavenge oxygen out. Also, if a lot of air is being dumped (from ventilation) the room needs to handle that airflow to avoid pressurizing the room or creating stagnation. In some cases, cooling the room is important too. Multiple chambers and compressors can heat a small room significantly. HVAC systems might need upsizing.

• Compressor and Gas Storage Placement: Noisy compressors and large oxygen tanks are often placed in a separate equipment room or outside shelter. This keeps noise away and isolates hazards (like an oxygen manifold) in a safer area. Oxygen storage (liquid or high-pressure cylinders) must follow codes: e.g., NFPA and CGA require cylinders to be secured, in ventilated areas, with proper signage and distance from flammables. Designers will create an oxygen supply panel typically with pressure regulators, emergency shutoff valves (often an E-stop outside the chamber room to cut oxygen supply in a fire), and flow controls. The medical gas room might also need gas detection (for oxygen leaks or compressor CO monitoring).

• Piping and Penetrations: Plumbing lines for air and O₂ run from the equipment room to the chamber. These should be sized for the flow required (a multi-place might need hundreds of liters per minute flow). All piping through walls should be in conduit or protected, and meet any building code for penetrations (like fire-stop material where they pass through fire-rated walls). Also, a grounding/bonding system is needed: the chamber, pipelines, and compressor should all be bonded to a common ground to prevent static and potential differences.

• Fire Suppression and Alarms: The facility’s fire alarm system should integrate the chamber room. If an alarm triggers (smoke or sprinkler flow in that room), protocols might call for cutting electrical power to the chamber (except lights/comms on UPS) and halting oxygen flow – some advanced installs have relays that do this automatically. Sprinkler heads in the room (and possibly a deluge inside chamber for Class A) must be in place as per NFPA. If using water mist inside the chamber, supply lines for that system (and a pump) are part of infrastructure.

• Utilities – Power and HVAC: As noted, a dedicated electrical feed, possibly 208–240V 3-phase for big compressors, is needed. Emergency generator backup should be wired for critical chamber functions. On HVAC, besides room AC, if the chamber itself has a built-in climate system (common in large multiplace units), condensers or chillers for it might sit outside. Water supply and drain might be needed if using a water jacket cooler or humidity control (some systems use chilled water to cool breathing air, meaning you need a source of chilled water or a dedicated chiller unit). If using a vacuum pump for drawing down masks (BIBS exhaust), that pump needs placement and maintenance space too.

• Installation Logistics: The chamber may be prefabricated in sections and need to be moved into place. Consider whether doors or walls need removal to get it in. Some are so large they are installed during building construction. If trailer-mounted (some hyperbaric units are in trailers for mobile use), then site prep (like level concrete pad, power hookup, and oxygen supply) is needed.

• Signage and Security: The facility should have proper warning signs (“Hyperbaric Oxygen: No Open Flames”, etc.) at chamber room entrances. Also, access control might be needed to prevent unauthorized personnel from entering the area or tampering with controls.

Designing the chamber in tandem with its support infrastructure ensures that once built, it can function as intended in its environment. Overlooking these aspects could lead to a chamber that’s fine on paper but problematic in practice (e.g., if an oxygen exhaust isn’t vented outdoors, the room could accumulate oxygen, a serious hazard). Therefore, considerations for compressors, gas storage, room construction, and utilities are just as important as the chamber itself. Hyperbaric facilities are essentially mini hospitals, combining mechanical systems, medical gas systems, and building systems; coordination among architects, engineers, and the chamber manufacturer is necessary to get everything right and compliant with building codes and safety standards.