The paper gives results of a study to provide data on industrial flare emissions. (Emissions of incompletely burned hydrocarbons from industrial flares may contribute to air pollution. Available data on flare emissions are sparse, and methods to sample operating flares are unavailable.) Tests were conducted on 3-, 6-, and 12-in. diameter flare heads. Propane was used as the flare fuel, diluted with nitrogen to control the heating value. The following results were obtained: (1) soot (from smoky flares) accounts for <0.5% of the unburned hydrocarbon emissions; (2) the size of the flare head did not influence hydrocarbon combustion efficiency; and (3) the stability of the flare flame influenced combustion efficiency, with unstable flames tending to promote inefficient combustion. A relationship between gas heating value and exit velocity was developed to denote the region of flame instability.