Table 2.

Factors affecting fire and explosion hazards posed by hydrogen, methane, propane, and acetylene at atmospheric conditions (1 atm and 298 K).

Factor	Hydrogen value	Ref.	Methane value	Ref.	Propane value	Ref.	Acetylene value	Ref.
LFL (V% fuel in air)	4.2	31	5	31	2.1	31	2.6	31
UFL (V% fuel in air)	74	31	14.9	31	9.5	31	80	31
MOC (V% oxygen)	4	31	12	31	11.6	31	6.2	31
Autoignition temperature (K)	858	36	813	37	757	38	578.15	39
Minimum spark ignition energy (mJ)	0.02	40	0.29	40	0.48	41	0.019	32
Density (kg/)	0.083	42	0.657	43	1.832	44	1.092	39
Molecular size (nm)	0.29	45	0.38	45	0.45	46	0.33	47
Quenching distance (mm)	0.64	48	2.03	48	2.0	49	0.53	50
Boiling point (K)	20.4	31	111.7	31	231.1	31	189.2	31
Flame speed at equivalence ratio of 1 (cm/s)	207	48	36	48	40.1	51	127.9	33
LHV (MJ/kg)	119.9	52	48.6	53	46.4	54	48.2	55
Adiabatic flame temperature in air (K)	2376	56	2223	56	2253	57	2500	58
Deflagration index (barm/s)	638	59	46	59	76	59	42	60
Thermal conductivity (W/(mK))	182.0	40	34.0	40	18.5	61	21.4	61