The evaporator pad in a fuel cell power unit installed in a hydrogen-powered forklift caught fire during operation. The evaporator pad is used for wicking the product water created by the fuel cell. The operator dismounted the forklift, observed flames coming from the fuel cell unit, and called for help. The facility fire brigade used a fire extinguisher to put out the fire. The upper left corner of the fuel cell evaporator pad was burned entirely; the plastic bracket that holds the evaporator pad in place was distorted; there was some discoloration of the radiator. No injuries were sustained by the operator and no damage was sustained by the forklift.
The fuel cell unit continued to run during the incident, as did the onboard data acquisition device. Hydrogen concentrations from an array of six hydrogen sensors around the unit during low and high duty cycles measured at less than 0.2%.
The root cause of the fire that burned the evaporator pad and distorted the plastic evaporator pad bracket remains unknown. The initial investigation did not reveal any obvious signs of an ignition source in the vicinity of the forklift operation. The on-board data acquisition system did not indicate any abnormalities in the operating parameters of the fuel cell system (e.g., temperature, pressure, voltage, current). The fuel cell was disassembled, but no evidence was found of any electrical shorts or other potential ignition sources. Thus it was concluded that the fuel cell unit itself was not the ignition source for this incident.
One theory presented the possibility of a spark (caused by static electricity) being the source of the ignition that caused the fire. Due to the proximity of the fuel cell unit to a shrink-wrap packaging machine at the time of the incident, this seemed to be a plausible hypothesis. However, sparking tests on evaporator pad materials failed to confirm this, and it seems highly unlikely that a wet evaporator pad would ignite from static electricity. The true ignition source for this incident remains unknown.
After the initial investigation, the company used a hydrogen meter to monitor hydrogen levels near the evaporator pad during fuel cell start-up (which they expected to be the highest, due to a system purge). They also wanted to investigate if hydrogen could become trapped near the vent covering the evaporator pad. The tests indicated hydrogen levels well below the lower flammability limit (0.022%). Similar readings were also detected from the exhaust on the other make/model fuel cells operating in the facility. They detected no sign that high levels of hydrogen were trapped near the vent of any fuel cell make/model.