UPDATE: A subsequent investigation by the University of California Center for Laboratory Safety determined that the cause of the explosion was an electrostatic spark, after laboratory testing ruled out a spark from the pressure gauge. Read the full story here

An explosion last month that caused a University of Hawaii, Manoa, postdoctoral researcher to lose an arm was caused by a spark from a digital pressure gauge that was not designed for use with flammable gases, says a Honolulu Fire Department investigation report.

Credit: Honolulu Fire Department

Thea Ekins-Coward was combining hydrogen, carbon dioxide, and oxygen gases from high-pressure cylinders into a lower pressure tank when the incident occurred. She has not given the university permission to release information about her condition, said spokesman Daniel Meisenzahl at an April 18 press conference.

The gas mixture was “food” for bacteria being used to produce biofuels and bioplastics. Ekins-Coward was working for the Hawaii Natural Energy Institute under researcher Jian Yu. A 2013 paper by Yu indicates a set-up in which gases are plumbed through a mixing device called a gas proportioner directly into the bioreactor (Int. J. Hydrogen Energy 2013, DOI: 10.1016/j.ijhydene.2013.04.153). The gas gauge identified in the paper is an “intrinsically safe” model designed to prevent ignition.

But after Ekins-Coward started in the lab last fall, she purchased a 49-L steel gas tank, a different gauge not rated as intrinsically safe, a pressure-relief valve, and fittings, and she put them together, Yu and Ekins-Coward told fire department investigators, according to the report. Ekins-Coward would add the gases to the portable tank, which would then be connected to the bioreactor. She was using a mixture of 70% hydrogen, 25% oxygen, and 5% carbon dioxide for her experiments, the report says.

In the week before the incident, a similar set-up with a 3.8-L tank resulted in a “small internal explosion” when Ekins-Coward pressed the off button on the gauge, the fire department report says. She also occasionally experienced static shocks when touching the tank, which was not grounded. She reported the shocks and possibly the small explosion to Yu, who told her not to worry about it, the report says.

On the day of the incident, the 49-L tank exploded when Ekins-Coward pressed the off button on the gauge. “She did not lose consciousness or hit her head; she was aware that she lost her arm in the explosion,” the report says. “She couldn’t open the door to the lab, the door was stuck closed.” Security officers and a graduate student kicked in the door to help Ekins-Coward get out. Her right arm was severed just above the elbow, the report says.

The University of Hawaii hired the University of California Center for Laboratory Safety to independently investigate the incident. That report is expected to be completed by the end of this month. The Hawaii Occupational Safety & Health Division is also investigating the incident.

Disaster Scene