Safe operation

A chamber is safe or unsafe as a system, not as a product. The same equipment, in the same room, with two different operating routines, produces two different risk profiles — and the difference is mostly in whether someone competent is outside the chamber, and whether the things brought inside it have been checked. This page sets out what the published record supports as a written operating procedure. It is not medical guidance and it does not tell you when to use a chamber.

Start from the manufacturer's instructions

FDA's first recommendation is to follow the manufacturer's instructions, "including reviewing operator manuals and instructions for use for information on device operation, maintenance, and fire prevention and safety measures" (FDA Letter to Health Care Providers, 25 August 2025). Your written procedure should be built from your manual, with this page as a cross-check for whether anything important is missing from it.

Supervision: the item the record argues hardest for

FDA recommends ensuring "the patient is properly monitored and supervised for the duration of the treatment" (FDA, 25 August 2025). UHMS recommends "that physicians or, as permitted by local regulations, supervised non-physician providers who are appropriately trained in Undersea and Hyperbaric Medicine, be available immediately throughout the administration of hyperbaric oxygen therapy," and states that "The UHMS does not endorse the concept of 'In Home' therapy at any time" (UHMS Position Statement, revised 10 July 2018).

The adverse-event record is consistent with those recommendations in a way that is difficult to read past. The two most recent death reports under product code CBF, both with event date 9 July 2025, describe flash fires during self-treatment in a sealed chamber; in one, the occupant had recently completed a safety and certification course (openFDA MAUDE death reports, product code CBF). MAUDE reports are unverified and a report is not a finding of cause. They are still the best public information available about how people have died using this equipment, and they point at unattended operation.

Pre-session: the prohibited-items and clothing check

FDA's recommendations include ensuring "prohibited items are not brought into the chamber, including electrical or static devices," and that clothing is "made of hyperbaric compatible materials … such as cotton," alongside awareness of "a heightened risk of fire with use of oxygen at a high concentration" and ensuring the device is properly grounded (FDA, 25 August 2025).

Two published mechanisms explain why this list is not arbitrary. Electrostatic sparks are a documented ignition source in hyperbaric oxygen (Ignition by electrostatic sparks in hyperbaric oxygen), and a study of skin care products in hyperbaric chambers reports greater flammability potential with increased oxygen fraction and pressure (flammability acceptability indices study). So the check covers both what the occupant carries and what is on their skin and hair.

Humidity belongs in the same check. UHMS notes ">60 percent humidity will nearly eliminate static potential," and that antistatic procedures are called for whenever chamber atmospheres exceed 23.5% oxygen, while Class A chambers are typically maintained below 23.5% oxygen with fire suppression installed (UHMS standards and codes FAQ). Record the room's relative humidity as part of the pre-session log.

Pre-session equipment verification

• Room temperature and relative humidity inside the published operating range — 50–100 °F and 30–90% RH at 77 °F for the Sechrist H-series (specifications), with UHMS reporting a 68–74 °F recommendation and seal performance affected below 50 °F (UHMS FAQ).
• Concentrator inside its own range of 41–95 °F, and delivering its published output — 2–9 L/min at 92% ±3%, 10 L/min at 90% ±3% for the AirSep NewLife Intensity 10 (specifications).
• Air supply pressure within requirement — 50.0–70.0 psi for the Sechrist H-series, with purge flow of 80–400 lpm at 15 psi (specifications).
• Window inspected. ASME PVHO-2 defines an Operational Visual Inspection as one of its two inspection levels, with the Maintenance Visual Inspection reserved for a qualified inspector (ASME PVHO-2-2019 preview pages).
• Breathing interface fitted and checked. Properly fitted masks produced 96–99% end-inspired oxygen while improperly fitted masks ranged 64–100% (PMID 871282); a delivery-systems study found acceptable inspired oxygen fraction reliably achieved with a continuously ventilated hood or a supervised demand-valve oral-nasal mask system (PMID 8931286).
• Communication method tested with the door closed, before pressurisation.
• Emergency stop and decompression path confirmed clear and known to the attendant.

Compression: go slowly and give the occupant control of the pace

Middle-ear barotrauma is the most commonly documented adverse effect and it happens principally during compression. Reported rates in supervised clinical settings include 262 cases among 2,610 patients over five years (PMID 32574438) and 68.7% of 67 users in an earlier report (PMID 8470522), with a review noting onset especially during compression (PMC4297009). One study found barotrauma in 10 of 11 subjects unable to autoinflate the middle ear, versus 7 of 19 who could (PMID 9331312).

Those are clinical figures and not a prediction for any individual. The operational conclusion they support: the occupant must be able to stop or slow compression at any moment, and that instruction has to be given before the door closes rather than assumed. Whether a particular person should be using a chamber at all, and what to do about equalisation difficulty, is a clinical question for a clinician — this site does not answer it.

During the session

• Attendant present and in communication, with no competing task.
• Ventilation running at the specified setting. Expect it to be loud: across 41 centres at 2.4 ATA, in-chamber levels ranged from 40.5 dB(A) without ventilation to 100.4 dB(A) with it (sound level study). Reducing ventilation to reduce noise trades a safety function for comfort — inadequate ventilation permits oxygen accumulation, which increases chamber fire risk (ventilation study).
• Gas schedule followed as documented. Published protocols include structured air breaks — two 45-minute oxygen periods separated by five minutes of air (PMID 17225483), three 20-minute periods (PMID 10517981), and 20-minute oxygen periods alternating with five-minute normoxic intervals at 2 ATA (PMID 863821). Air breaks are part of a protocol, not optional.
• Log pressure, gas settings and time. A cycle log is also what you need for the window service-life question under ASME PVHO-2.
• Stop for any occupant discomfort, any equipment behaviour that departs from specification, any smell of burning, and any electrical symptom — see troubleshooting.

After the session

• Decompress per the manufacturer's documented procedure. Note that the Sechrist H-series' published figure of 30 psig to 0 in a maximum of 119 seconds is an emergency vent capability, not a normal decompression schedule (specifications).
• Complete the session log: date, occupant, pressure, duration, gas settings, room conditions, attendant, and anything unusual.
• Clean using only manufacturer-approved products — cleaning agents are materials introduced into an enriched atmosphere, and flammability potential increases with oxygen fraction and pressure (PMID 18349735).
• Visual check of window, seals, hoses and cables before the chamber is put away or left for the next session.

What this page will not tell you

It will not tell you what pressure to use, how long a session should be, how often to have sessions, or whether a chamber is appropriate for any condition. Those are clinical decisions, hyperbaric chambers are prescription devices (FDA CDRH letter, 22 August 2013), and the settings that appear in published research are the researchers' protocols, not prescriptions — see what the published research actually used.

It also will not tell you that a lower-pressure chamber removes the need for any of the above. The ignition-source and oxygen-fraction issues are governed by the atmosphere the occupant is in, not by the number on the gauge, and UHMS's 23.5% oxygen threshold for antistatic procedures is stated without reference to chamber pressure (UHMS standards and codes FAQ).