fire from the evaporating pad of a fuel cells forklift

A fire developed on the fuel cells system installed of a hydrogen-powered forklift. The evaporator pad in caught fire during operation. The operator dismounted the forklift, noted 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 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 less than 0.2%

[Note of HIAD event validator: the H2TOOLS does not specify the unit of the values measured by the sensors. Later in the text, hydrogen concentration values are given in % of the Low Flammability Level (LFL) of hydrogen in air].

The INITIATING CAUSE was the ignition of an unknown quantity of hydrogen in or near the evaporating pad.
The ignition source and the root cause(s) are unknown.

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).
After the initial investigation, the company used a hydrogen meter to monitor hydrogen levels near the evaporator pad during fuel cell start-up (expected to cause the highest hydrogen concentration in air, due to a system purge). They also investigated if hydrogen could become trapped near the vent covering the evaporator pad. The tests indicated hydrogen levels well below the LFL (0.022%). Similar readings were also detected from the exhaust on the other make/model fuel cells operating in the facility. There was also no sign of high levels of hydrogen trapped near the vent stack of any fuel cell make/model.

evaporation pad,
PEMFC

DESCRIPTION OF THE EVAPORATING PAD
In a fuel cell system, particularly in Polymer Electrolyte Membrane (PEM) fuel cells, an evaporating pad is used for managing water and heat simultaneously. It functions by absorbing water and allowing it to evaporate into the gas streams (anode or cathode), thereby providing essential membrane humidification and removing waste heat. It is often part of an evaporative cooling or internal humidification system.