TITLE:	ES&H Manual
DOCUMENT ID:	6152 Appendix R2 Heats of Combustion

Hydrogen equivalent, Q

The heat of combustion for other gases is used to determine the hydrogen equivalent mass, Q, for use in Figure 1 in ES&H Manual Chapter 6152 Storage/Use of Flammable Gases. For example the table indicates that ethane has 0.36 times the heat of combustion of hydrogen per unit mass. Therefore 1.7 kg of ethane is equivalent to 0.6 kg of hydrogen in determining Risk Class.

Heats of Combustion

The following table of heats of combustion may be useful for calculating hydrogen equivalents. The heats of combustion can be found in, for example, The Handbook of Chemistry and Physics, 77th Edition, 1997.

		gross heat of combustion
Gas	molecular weight	(kj/g)	relative to that of hydrogen
hydrogen-H2	2	143	1.00
deuterium- D2	4	72	.50
methane-CH4	16	55	.39
acetylene-C2H2	26	50	.35
ethane-C2H6	30	51	.36
propane-C3H8	44	50	.35
isobutane-C4H10	58	49	.34
dimethyl ether- (CH3)2O	46	32	.22

ISSUING AUTHORITY	APPENDIX AUTHOR	APPROVAL DATE	EFFECTIVE DATE	EXPIRATION DATE	REV.
ESH&Q Division	Bert Manzlak	01/26/05	01/26/05	01/26/08	0

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