Combustion properties of paraffins and alkanes.
Paraffin / Alkane	Chemical Formula	Higher Heating Value(Btu/lbm)	Air/Fuel Ratio	Max Flame Speed(ft/s)	Adiabatic Flame Temp.(°F)	Ignition Temp.(°F)	Flash Point(°F)	LEL(% vol)	UEL(% vol)
Ethane	C₂H₆	22323	15.899	1.3	3540	968 - 1166	*)	3	12.5
Methane	CH₄	23875	17.195	1.1	3484	1301	*)	5	15
Propane	C₃H₈	21669	15.246	1.3	3573	871	*)	2.1	10.1
n-Butane	C₄H₁₀	21321	14.984	1.2	3583	761	-76	1.9	8.4
iso-Butane	C₄H₁₀	21271	14.984	1.2	3583	864	-117	1.8	8.4
n-Pentane	C₅H₁₂	21095	15.323	1.3	4050	588	< -40	1.4	7.8
iso-Pentane	C₅H₁₂	21047	15.323	1.2	4055	788	< -60	1.3	9.2
Neopentane	C₅H₁₂	20978	15.323	1.1	4060	842	*)	1.4	7.2
n-Hexane	C₆H₁₄	20966	15.238	1.3	4030	478	-7	1.3	7
Neohexane	C₆H₁₄	20931	15.238	1.2	4055	797	-54	1.2	7.6
n-Heptane	C₇H₁₆	20854	14.141	1.3	3985	433	25	1	6
n-Octane	C₈H₁₈	20796	15.093	—	—	428	56	0.9	3.2
iso-Octane	C₈H₁₈	20770	15.093	1.1	—	837	10	0.8	5.9

Source: engineeringtoolbox.com

Unit Conversion Factors

The following conversion factors are essential for working with the data in different unit systems.

$T(°C) = \frac{5}{9} (T(°F) - 32)$

$1 \, \text{ft/s} = 0.3048 \, \text{m/s}$

$1 \, \text{Btu/lbm} = 2{,}326.1 \, \text{J/kg} = 0.55556 \, \text{kcal/kg}$

Notes & Definitions

LEL: Lower Explosive (or Flammable) Limit. The minimum concentration of a combustible gas or vapor in air that will ignite and burn if an ignition source is present.
UEL: Upper Explosive (or Flammable) Limit. The maximum concentration that will ignite.
*): In the original table, this notation typically indicates the property is for the gas form of the substance at standard conditions.