A dust collection system has a cyclone separator in which dust is separated from an air stream and the air stream is passed from a separator and flows through a final filter back into the ambient air. A flame arrester is positioned downstream of the separator, either in advance of or after the final filter. The flame arrester defines a multiplicity of narrow channels to permit exhaust air flow but block any flame front. In a preferred embodiment the flame arrester is in the form of a sheath of a porous metal material surrounding the final filter. The sheath may comprise a metal wire mesh screen, with a guard cage surrounding the screen.