Compared to gasoline, hydrogen is lightweight, has a higher energy density and has a variety of potential sources, like biomass. It sounds great, but there are a few drawbacks. Hydrogen-air mixtures can ignite with very low energy input. If air and hydrogen were to mix in an enclosed space, like a parking lot, a hydrogen leak could easily lead to an explosion if a flame was sparked. Due to hydrogen’s low energy ignition, hydrogen must be safely and densely stored.