Part of the classification system used by the National Electrical Code (NFPA 70) to describe the fire or explosion hazard present in a specific area.
A Class I, Division 1 location in which: ignitable concentrations of flammable gases or vapors can exist under normal operating conditions; ignitable concentrations of such gases or vapors may exist frequently because of repair or maintenance operations or because of leakage; or a breakdown or faulty operation of equipment or processes might release ignitable concentrations of flammable gases or vapors and might also cause simultaneous failure of electric equipment.
See also PEI/RP500.
