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The quenching of flames propagating in vapour/air mixtures of seven different solvents is compared with that of propane flames, reported previously, and with that of ethylene flames. The arresters were perforated sheets and blocks, and were mounted in a horizontal explosion tube; all the solvents were of types in common industrial use. Measurements of flame velocities showed that the ease of quenching of flames propagating in the solvent/air mixtures was similar to that of propane flames propagating at the same velocity. Thus when a flame arrester is installed in an industrial plant dealing with several vapours, the design of the arrester can be based on the range of flame velocities to be expected and the variations in the thermal properties of the flames can be ignored. The experiments with ethylene flames showed that if the apertures in the arrester were nearly as large as the quenching diameter, the effectiveness of the arrester was low. This is discussed on a theoretical basis. The ease of quenching of cool flames propagating in horizontal or vertical tubes was about the same as that of ordinary hot flames propagating at the same velocity. Arresters designed for ordinary flames would be capable of quenching cool flames.