An independent investigation into an ambulance fire on Aug. 24, 2022 that left a patient dead determined it was most likely started from an oxygen tank and regulator, which controls the pressure of the oxygen coming out of the tank. However, the “precise mechanism” that triggered the fire remains unknown, the report said.
The ambulance caught on fire and became engulfed in flames as it was pulling up to Adventist Health Castle hospital in Kailua. The fire killed Fred Kaneshiro, a 91-year-old patient, and critically injured Jeff Wilkinson, a 36-year-old paramedic.
The report was conducted by the Emergency Care Research Institute, an independent nonprofit focused on health care technology and safety, and sent to Spectrum News Hawaii by the Honolulu Emergency Services Department.
As the ambulance approached the hospital, the paramedic switched the patient’s oxygen source from the ambulance tank to a portable tank in order to transfer the patient to the emergency room. The report said the fire most likely started within the portable oxygen tank's regulator, as two connectors were pushed together. The connectors were not recovered, so it is unknown if they latched, but oxygen flow begins before latching occurs, according to the report.
“Due to high internal pressure and pure oxygen within the regulator, the fire burned very quickly (i.e. milliseconds) leading to an explosion that created the holes in the aluminum body … the holes in the regulator allowed the fire to escape. Now amplified by 100% oxygen under high pressure acting as the oxidizer, the oxygen cylinder and regulator assembly acted like (a) large flamethrower igniting surrounding materials easily and quickly,” the report said.
The report said what caused the fire within the regulator remains unknown. Two mechanisms are known to cause regulator fires, both of which involve contaminants, like small amounts of oil and grease, organic and metallic substances, within the oxygen tank and regulator assembly that burn when exposed to high pressure and heat in an oxygen-enriched environment.
The first is known as adiabatic compression or the “gas hammer effect,” which occurs when oxygen rushes into the regulator stem, creating a spike in pressure and heat with an oxygen-enriched environment. These conditions can ignite contaminants within the system.
The second is known as particle impacts, and it occurs when oxygen swiftly flows out of the oxygen tank and regulator. This action can propel contaminants and metal flakes from within the oxygen tank with enough force to ignite other objects when they slam into them.
The report said oxygen regulator fires are rare, but have caused injuries for other paramedics, EMTS and firefighters over the years.
Michelle Broder Van Dyke covers the Hawaiian Islands for Spectrum News Hawaii. Email her at michelle.brodervandyke@charter.com.
