Fabric dust collectors are associated with the risk of exlosion because of the large volumes of dust containing gases processed. Vent devices that open when the internal pressure exceeds a preselected level control this risk. The National Fire Protection Association publishes standards for the selection sizing, and placing of these vents. For chemical engineers, the most relevant standards are those that describe high strength enclosures in which the operating pressure is less than 0.2 bar gage; the gas that contains potentially explosive dust is air; and the length to diameter ratio is less than 5.