ELK Map gas is a mixture of various hydrocarbon, principally, methylacetylene and propadiene. Map gas is a mixture of various hydrocarbons, principally, ... 3 ) but much higher than for propane (10,433kJm 3 ). The secondary flame (outer cone) also gives off a high heat ... release, similar to propane and natural gas. The combination of a lower flame temperature, more distributed heat source and larger ...