Fire Potential in HBO Chambers

The above referenced paper analyzes fires in chambers reported in Asia, Europe, and North America from 1923 to 1996.  Information was gathered both from reports in the literature and from the Undersea and Hyperbaric Medical Society (UHMS) Chamber Experience and Mishap Database.  The UHMS database contains reports of fire, structural failure, and other operator experience.  Strong fire safety codes now govern hyperbaric facilities in the United States.  European facilities also have strong regulatory standards. Twenty-five fires occurred in clinical hyperbaric chambers during the above time frame, and these were mostly in China.

Three components must be present for a fire to occur:  ignition, oxygen, and fuel (burnable material).  Fire behaves differently with varying oxygen concentration.  Combustion can occur if O2 is above 12 %.  The fire safety standard for hyperbaric chambers NFPA 99 Chapter 19 defines an oxygen-enriched atmosphere as “an atmosphere in which the concentration of O2 exceeds 23.5 % by volume.” Within an oxygen-enriched hyperbaric chamber ignition energies are lower, the flame spread rate is faster, and the rise in temperature also causes a rapid rise in chamber pressure, and therefore problems of timely escape from the confined area.  Thus fire prevention is of the utmost importance. Medical and technical personnel who operate these facilities should know the potential for fire and implement protocols for its prevention. And, these personnel do know procedural codes in any properly regulated HBOT chamber provider, be it hospital or free-standing clinic.

Of the fires reported in this paper 25 occurred in clinical hyperbaric chambers.  Other chambers covered were diving and hypobaric (altitude) systems.

NFPA 99 forbids pressurization with pure O2 in multiplace chambers.  However, this practice has not been universal; three fires in China reportedly occurred in multiplace pure-oxygen chambers, resulting in 15 fatalities.

During the period 1967-1996, there were 60 fatalities in 21 of the 24 clinical hyperbaric chamber fires.  Ten fires were caused by ignition sources that occupants brought into the chamber such as hand warmers, lit cigarette, and spark generating toys.  Seven were thought to be caused by electrostatic sparks, five were caused by electrical ignition and two had unknown causes.

One fire was caused by a patient’s synthetic blanket, where the flames rapidly spread and the chamber exploded, killing the patient’s wife outside.  Other reports of fire were caused by static electricity from wool and synthetic fabrics. In this paper of the reviews of fires, a significant source of ignition was static electricity.

Severe burns caused most fatalities.  Carbon monoxide poisoning as well as toxic gases are other factors that contributed to the deaths.

The 73-year analysis of clinical HBOT experience shows no fatalities from fire in clinical hyperbaric chambers in North America.  European facilities reported two fatalities. Nineteen incidents occurred in Asia, resulting in 58 fatalities. However, in May 2010 a four-year-old Italian boy and his grandmother were severely burned in an explosion of a hyperbaric chamber at the Neubauer clinic in Florida.  The grandmother died the day after the explosion.  The boy, who was receiving HBOT for cerebral palsy, died a month later with burns over 90% of his body.

Reasonable precautions to prevent electrostatic sparks make good sense.  Synthetics and wool fibers that can build up static charge should not be permitted in the chamber.  Maintaining humidity above 50-60% reduces static sparks in the chamber, and humidifying the O2 before it reaches the patient reduces the amount of static electricity in the BIBS used for O2 delivery.

Titanium in watches, jewelry, and eyeglasses has a strong potential for ignition. Personnel should be vigilant in making sure patients do not enter the HBOT chamber with any titanium on their persons.33

Notes
33Titanium and HBO Fire Risk, Hink and Jansen,http://hbotechblog.files.wordpress.com/2009/07/titaniumandhyperbaric.pdf