Material Demands for Storage Technologies in a Hydrogen Economy

Table 2

Comparison of fuel safety properties in air [18, 24, 25, 27].

Fuel	Autoignition temperature	Flammable limits	Explosive limits	Buoyant velocity	Ignition energy^a
	K	Vol.%	Vol.%	m s^−1	mJ
Hydrogen	673–858	4.1−74.2	18.3−59.0	1.2–9.0	10
Methane	923	5.3−15.0	6.3−13.5	0.8–6.0	20
Ethane	788	3.0−12.5	—	—^b	—
Propane	723	2.3−9.5	3.1−7.0	—^b	—
Butane	678	1.9−8.5	—	—^b	—
Gasoline	553–729	1.4−7.6	1.1−3.3	—^b	—
Ethanol	696	3.3−19.0	—	—^b	—
Methanol	743	6.0−36.5	—	—^b	—

aIgnition energy at the lower flammability limit. For stoichiometric mixtures, the value is significantly lower (e.g., 0.02 mJ for hydrogen) [18].
bNonbuoyant, due to higher density than air (1.2 kg m⁻³) under standard conditions.