Ventilation and safety

Oxygen does not burn. It makes other things burn faster, hotter and at lower ignition energies, and a chamber's job is to concentrate it. Everything on this page follows from that one fact. It is also the page where the record is most serious: FDA has published reports of fires with injuries and deaths, and the most recent death reports in its adverse-event database involve unattended self-treatment.

What FDA said in August 2025

"The FDA is aware of reports of serious injuries and deaths with use of HBOT devices." And: "The FDA is aware of recent reports of fires that occurred with HBOT devices that resulted in serious injuries and deaths. Currently, the root cause of these events is not known. While the FDA believes that serious adverse events associated with HBOT devices are rare, health care providers and users should be aware that these events can and do occur."

Its recommendations, quoted from the same letter: review operator manuals and instructions for use for device operation, maintenance, and fire prevention and safety measures; be aware that there is "a heightened risk of fire with use of oxygen at a high concentration"; ensure the device is properly grounded; ensure staff training is maintained; control prohibited items "including electrical or static devices"; ensure clothing is "made of hyperbaric compatible materials … such as cotton"; and ensure "the patient is properly monitored and supervised for the duration of the treatment" (FDA Letter to Health Care Providers, 25 August 2025).

The adverse-event record

Twelve death reports are indexed under product code CBF in FDA's MAUDE database. The two most recent share an event date of 9 July 2025 and the same chamber model. One describes a person "found deceased inside of a hyperbaric oxygen chamber at his health clinic," with responders determining "that a flash fire occurred while [he] had been undergoing self-treatment inside the sealed chamber." The other describes "a male clinic founder [who] died in a flash fire inside an OxyHealth Fortius 420 hyperbaric chamber during self-treatment," noting he had recently completed a safety and certification course (openFDA MAUDE death reports, product code CBF).

MAUDE reports are voluntary and unverified, and a report is not a determination of cause. What they establish is a pattern worth designing against: self-treatment, sealed chamber, no one outside able to act, and in one case a trained occupant. Training does not substitute for an attendant.

Ventilation is a measurable safety control

Chamber ventilation is not comfort management. A study of hyperbaric chamber ventilation measured local underventilation at multiple pressures and states that oxygen accumulation can increase chamber fire risk (Effectiveness of hyperbaric chamber ventilation). That is the mechanism: an inadequately ventilated volume enriches, and an enriched volume ignites more readily.

Manufacturers publish purge rates for exactly this reason. The Sechrist H-series specifies a purge flow of 80–400 litres per minute at 15 psi, a supply pressure of 50.0–70.0 psi, and an emergency vent capability taking the chamber from 30 psig to 0 in a maximum of 119 seconds, with two relief valves set at 35.00 psi on the 3300H and 36.00 psi on the 3600H and 4100H (Sechrist H-series specifications). Those are the numbers that make purge and emergency decompression verifiable rather than assumed.

Ventilation has a cost, and it is audible. Across 41 hyperbaric centres operating at 2.4 ATA, the highest equivalent continuous sound level recorded was 100.4 dB(A) with ventilation running, and the lowest was 40.5 dB(A) without it (Evaluation of in-chamber sound levels during hyperbaric oxygen applications: results of 41 centres). Those are clinical-centre measurements, not a prediction for any particular installation, but they show that the quiet configuration and the well-ventilated configuration are not the same configuration. Ask to hear the system running with ventilation at operating settings before you buy.

Oxygen fraction thresholds and antistatic practice

UHMS's standards FAQ gives the working thresholds: antistatic procedures are called for whenever chamber atmospheres exceed 23.5% oxygen; Class A chambers are typically maintained below 23.5% oxygen with fire suppression installed; and ">60 percent humidity will nearly eliminate static potential" (UHMS standards and codes FAQ).

The 23.5% figure is the one to hold on to, because it reframes the whole "mild is safer" argument. The question is not the chamber's pressure. It is whether the atmosphere the occupant is sitting in exceeds 23.5% oxygen — which depends on what is being fed into the chamber and how well it is being purged, not on the number on the pressure gauge.

Ignition sources, from the published literature

Electrostatic sparks are a documented ignition mechanism in hyperbaric oxygen (Ignition by electrostatic sparks in hyperbaric oxygen). A study of skin care products in hyperbaric chambers reports greater flammability potential with increased oxygen fraction and pressure, and exists precisely because ordinary consumer products behave differently in an enriched atmosphere (Selection of skin care products for use in hyperbaric chambers and flammability acceptability indices).

Combine that with FDA's recommendations on prohibited items and cotton clothing (FDA, 25 August 2025) and the practical list writes itself: no phones, no e-readers, no battery devices, no heated or electronic items, no synthetic clothing where cotton is specified, and no lotions, ointments, hair products or cosmetics that have not been assessed for use in the chamber. This is not fussiness. It is the whole ignition-source control programme.

Fire protection for the room

For chambers installed in buildings, NFPA 99 Chapter 14 requires that a sprinkler system installed to NFPA 13 or a water mist system installed to NFPA 750 "shall be installed in the room housing a Class A, Class B, or Class C chamber and in any ancillary equipment rooms." Class A chambers and all ancillary service equipment "shall be protected by 2-hour fire-resistant-rated construction," while Class B and C chambers inside a building are not required to have that rating. The room housing a Class A or Class B chamber "shall be for the exclusive use of the hyperbaric operation" (NFPA 99, 2015 edition, clauses 14.1.2.2, 14.2.1.1, 14.2.1.1.2, 14.2.1.1.7, 14.2.1.2). The enforceable edition is the one your authority having jurisdiction has adopted, and you should confirm which that is early. NFPA has published on fire protection for hyperbaric facilities in hospitals and identifies Chapter 14 as the governing text (NFPA Journal).

What a buyer should require before delivery

• The manufacturer's operator manual and instructions for use, in hand, before purchase.
• Published purge flow, supply pressure requirement, relief-valve settings and emergency vent capability for the exact model.
• A written statement of the maximum oxygen fraction the chamber atmosphere will reach in the intended configuration, and how it is purged.
• The grounding requirement and how it will be satisfied in your room.
• A written prohibited-items list and a clothing requirement, to be posted at the chamber.
• A written attendant requirement, and a stated procedure for stopping a session.
• For commercial installations: NFPA 99 class, suppression design, exclusive-use room confirmation, and the AHJ's adopted edition.

Safe operation covers the running procedure itself. Anyone who tells you a lower-pressure chamber removes the need for this list is not reading the same sources we are.