Maximum experimental safe gap

Maximum experimental safe gap (MESG) is a standardized measurement of how easily a gas flame will pass through a narrow gap bordered by heat-absorbing metal. MESG is used to classify flammable gases for the design and/or selection of electrical equipment in hazardous areas, and flame arrestor devices. The National Electrical Code classifies Class I hazardous locations into different groups depending on the respective MESG's of gases in the area.

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