A preliminary investigation into an August ambulance explosion in Hawaii points to a portable oxygen tank and regulator mechanism as the location of the explosion.

Now investigators are looking into what may have ignited that oxygen. Fill Propane Tank

The Aug. 24 fire killed a 91-year-old patient and severely injured a 36-year-old paramedic when flames engulfed the back of the ambulance in the parking lot of a Kailua’s Adventist Health Castle hospital.

The paramedic was using a CPAP device to maintain oxygen supply to the patient. As the ambulance approached the hospital, he disconnected the CPAP device from the wall oxygen port and was connecting it to the portable oxygen cylinder to prepare the patient for transfer to the hospital.

That’s when the paramedic heard a pop and saw a flash of light. Though the location of the explosion has been determined, the initial investigation by ECRI did not uncover any source of ignition, such as a static electricity spark or a spark from a piece of equipment, Dr. Jim Ireland, EMS director said.

Portable Oxygen Cylinder The investigation did rule out any fire in any of the other equipment in the ambulance as a possible source. Three Honolulu EMS ambulances similar to the one involved in the fire remain out of service as a precaution while the investigation is concluded.