Coffee Break Training: Inspection Techniques: Electrical 'Classified Locations': Gas and Vapor 'Material Groups' (Part 7) [open pdf - 351KB]
"Coffee Break Training FP-2011-20 introduced the overall framework of hazardous electrical locations, and the following week explained generic Class I locations for flammable liquids and gases. Today, we go into more detail in describing Class I 'material groups.' The explosive characteristics of gas- or vapor-air mixes differ depending upon the specific product involved. For Class I locations, the classification involves an analysis of the potential maximum explosion pressure of a vapor- or gas-air mixture, and an assessment of the likelihood that specific electric equipment will cause an ignition under a variety of conditions."
Coffee Break Training - Fire Protection Series No. FP-2011-25
United States Fire Administration: http://www.usfa.fema.gov/