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Chapter 8 Area Classification IHazardous Area Classifications andProtectionsThe intent of this document is to provide a broadoverview of hazardous area classifications and the

types of protection techniques involved. Theinformation provided in this bulletin is for educationalpurposes and should not be used in place of any othersource or governing documents.Not all approvals are covered in this bulletin. Contactyour Emerson Process Management sales office forinformation on approvals not covered in this bulletin.Contact your Emerson Process Management salesoffice for product specific hazardous area approvalinformation or visit our website at www.Fisher.com.Hazardous AreaClassificationsWhen electrical equipment is used in, around, or nearan atmosphere that has flammable gases or vapors,flammable liquids, combustible dusts, ignitable fibersor flyings, there is always a possibility or risk that a fireor explosion might occur. Those areas where thepossibility or risk of fire or explosion might occur dueto an explosive atmosphere and/or mixture is oftencalled a hazardous (or classified) location/area.Currently there are two systems used to classify thesehazardous areas; the Class/Division system and theZone system. The Class/Division system is usedpredominately in the United States and Canada,whereas the rest of the world generally uses the Zonesystem.Class/Division SystemHazardous locations per the Class/Division system areclassified according to the Class, Division, and Group.1. ClassThe Class defines the general nature (orproperties) of the hazardous material in thesurrounding atmosphere which may or may not be insufficient quantities.a. Class ILocations in which flammable gases orvapors may or may not be in sufficient quantities toproduce explosive or ignitable mixtures.b. Class IILocations in which combustible dusts(either in suspension, intermittently, orperiodically) may or may not be in sufficientquantities to produce explosive or ignitablemixtures.

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c. Class IIILocations in which ignitable fibers mayor may not be in sufficient quantities to produceexplosive or ignitable mixtures.2. DivisionThe Division defines the probability of thehazardous material being able to produce an explosiveor ignitable mixture based upon its presence.a. Division 1 indicates that the hazardous materialhas a high probability of producing an explosive orignitable mixture due to it being presentcontinuously, intermittently, or periodically or fromthe equipment itself under normal operatingconditions.b. Division 2 indicates that the hazardous materialhas a low probability of producing an explosive orignitable mixture and is present only duringabnormal conditions for a short period of time.3. GroupThe Group defines the type of hazardousmaterial in the surrounding atmosphere. Groups A, B,C, and D are for gases (Class I only) while groups E, F,and G are for dusts and flyings (Class II or III).a. Group AAtmospheres containing acetylene.b. Group BAtmospheres containing a flammablegas, flammable liquid-produced vapor, orcombustible liquid-produced vapor whose MESG isless than 0.45 mm or MIC ratio is less than 0.40.