It‘s cleaner than diesel or gasoline. Hydrogen use in fuel cell vehicles eliminates tailpipe emissions of toxic compounds. In a hydrogen fuel cell vehicle, hydrogen (H2) combines with oxygen (O) to make water and electricity. While hydrogen is flammable, it is non-toxic and emits zero pollutants when used in a fuel cell. And if there's ever a leak in a hydrogen tank, the hydrogen dissipates quickly into the surrounding air, decreasing fire hazard and pollution risk.