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NOTE: This is an unformatted excerpt from our online fire protection training library.

Identifying Materials & Equipment

Liquids, Vapors & Gases

Group Classification

Historically, flammable liquids, gases, and vapors have been assigned to groups based on their MESGs, explosion pressures, and ignition temperatures. Some materials have retained the groupings originally assigned Acetylene is the primary example, as it is the only member of Group A even though its MESG and MIC ratio fit into Group B. based on these issues. However, the definitions of the groups now are based on MESGs and MIC Ratios. Both the Division The Groups used under the division classification system are A, B, C, and D, arranged in decreasing order of hazard. and Zone The Groups used under the zone classification system are IIC, IIB, and IIA, arranged in decreasing order of hazard. grouping systems are based on these values now. Considerations such as extreme explosion pressures Acetylene retains its own group primarily because of its extreme explosion pressure. or dramatic effects of pressure piling are still used to modify the groupings in some cases.
NOTE: This is an unformatted excerpt from our online fire protection training library.

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