Safety Evaluation on Fuel Cell Stacks Fire and Toxicity Evaluation of Material Combustion Gas for FCV 2007-01-0435

Fuel cell vehicles represent a new system, and their safety has not yet been fully proved comparing with present automobile. Thorough safety evaluation is especially needed for the fuel system, which uses hydrogen as fuel, and the electric system, which uses a lot of electricity. The fuel cell stacks that are to be loaded on fuel cell vehicles generate electricity by reacting hydrogen and oxygen through electrolytic polymer membranes which is very thin. The safety of the fuel and electric systems should also be assessed for any abnormality that may be caused by electrolytic polymer membranes for any reasons. The purpose of our tests is to collect basic data to ultimately establish safety standards for fuel cell stacks. Methanol pool flame exposure tests were conducted on stationary use fuel cell stacks of two 200W to evaluate safety in the event of a fire.

Small parts of the separators spattered in one flame exposure the test and the depression of separators by combustion was observed in another one. However, no abnormalities, such as explosion caused by reaction hydrogen gas and oxygen in air or electrical short-circuiting, were observed in either test.

And, also the gas analysis were also conducted on combustion gases of the materials of the fuel cell stack, the high-pressure fuel tanks and the electric wires etc., to collect basic data to evaluate the toxicity of combustion gases when fuel cell vehicles are exposed to fire. Qualitative and quantitative analyses were conducted in this test on a total of 23 components from among the gases specified by the American Conference of Governmental Industrial Hygienists (ACGIH) as being harmful to human health, including 21 components of available standard gas as well as carbon monoxide and carbon dioxide.

A high concentration (696 ppm) of sulfur dioxide was detected in combustion gas from the ion exchange membrane. This was dependent on the inclusion of sulfur trioxide in the ion-exchange membrane and the change into sulfur dioxide by the burning reaction.

Gases with concentrations exceeding the concentration American Conference of Governmental Industrial Hygienists (ACGIH) were also detected in the combustion gases from the O ring, gasket, low-voltage and high-voltage electric wires, and high-pressure fuel tank. However, it did not reach a concentration level that would immediately threaten human life.