MESG is the Maximum Experimental Safe Gap. This is the maximum clearance between two parallel METAL SURFACES that has been found, under special test conditions, to PREVENT an explosion in a test chamber from being PROPAGATED to a secondary chamber containing the same gas or vapor at the same concentration. In the “Class/Division/Group system of hazardous area classifications, MESG distance values (in mm) are used for Groups B, C, and D, to define the types of hazardous gases in the SURROUNDING atmosphere.

MESG is the Maximum Experimental Safe Gap. This is the maximum clearance between two parallel metal surfaces that has been found, under special test conditions, to prevent an explosion in a test chamber from being propagated to a secondary chamber containing the same gas or vapor at the same concentration. In the “Class/Division/Group system of hazardous area classifications, MESG distance values (in mm) are used for Groups B, C, and D, to define the types of hazardous gases in the surrounding atmosphere.