Quarried rock products for road-stone or cement manufacture provide the most commonly met crusher applications although crushing of coal and metallic ores a regularly met also. Slow acting large capacity crushers such as jaw crushers and cone crushers are fairly straightforward to treat with extraction applied at the point where the crushed product exits the crusher discharge chute. High speed impact crushers and hammer mills are more problematic since they have a tendency to act as a fan especially when not choke fed. Choke feeding reduces the amount of air they can draw in and then eject as a dust cloud on the discharge side so any exit side dust extraction must take account of the air rush or wind created. Larger installation will need a pulse jet bag filter such as the FabriPulse Fusion although OptiFlo RC also applies. Collectors dealing with coal and other combustibles will need explosion relief.