ARTICLE HAZARDOUS CLASSIFIED LOCATIONS

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500 1 Hazardous Classified Locations,Article 511 Commercial Garages Repair and Storage. 500 1 Scope Articles 500 Through 504 Article 513 Aircraft Hangars. Article 514 Motor Fuel Dispensing Facilities, To prevent injury death or extensive damage to structures from fires Article 515 Bulk Storage Plants. or explosions the NEC contains stringent requirements for equip Article 516 Spray Application Dipping and Coating. ment and its installation in hazardous classified locations where fire Processes. or explosion hazards may exist due to flammable gases flammable Article 517 Health Care Facilities. liquid produced vapors combustible liquid produced vapors combus. tible dusts or fibers flyings The specific requirements for electrical. installations in hazardous classified locations are contained in 500 2 Definitions. Article 501 Class I Flammable or Combustible, Liquid Produced Vapors or Flammable Gases The definitions contained in 500 2 apply to Articles 500 through 504. Article 502 Class II Combustible Dust and Articles 510 through 516. Article 503 Class III Easily Ignitible Fibers Flyings. Combustible Dust Dust particles that are 500 microns or smaller and. Article 504 Intrinsically Safe Systems, present a fire or explosion hazard when dispersed and ignited in air. Author s Comment,Author s Comment,n See the definition of Structure in Article 100.
n The size of the material may be a significant factor in distin. n Locating electrical wiring and equipment outside a classified guishing dust Class II from fibers and flyings Class III. location provides the safest electrical installation and is often. more cost effective 500 5 A Note Dust Ignitionproof Equipment enclosed in a manner that excludes. dust and doesn t permit arcs sparks or heat inside the enclosure to. n Many of the graphics contained in Chapter 5 use two shades. ignite accumulations or suspensions of a specified dust on or in the. of red to identify a Division location darker red for Division 1. vicinity of the enclosure, and lighter red to identify Division 2 In some cases these. color schemes are used as a background color to help you Dusttight Enclosures constructed so that dust won t enter under. tell if the graphic applies to Division 1 Division 2 or both specific test conditions Examples of dusttight enclosures include FS. split color background boxes and bell boxes Figure 500 2. n The NEC doesn t classify specific hazardous classified. locations except as identified in Articles 511 through 517. Determining the classification of a specific hazardous area is. the responsibility of those who understand the dangers of the. products being used such as the fire marshal plant facility. engineer or insurance underwriter It isn t the responsibility. of the electrical designer electrical contractor or electrical. inspector Prior to performing any wiring in or near a hazard. ous classified location contact the plant facility and design. engineer to ensure that proper installation and materials are. used Be sure to review 500 4 B for additional standards. that might need to be consulted, Other articles in Chapter 5 containing specific hazardous installation. requirements include, Article 505 Class I Zone 0 1 and 2 Locations Figure 500 2. 24 Mike Holt s Illustrated Guide to Hazardous Locations based on the 2014 National Electrical Code. Hazardous Classified Locations 500 4, Hermetically Sealed Equipment sealed against the entrance of an. external atmosphere Figure 500 3 500 4 General, A Classification Documentation All hazardous classified locations.
must be properly documented The documentation must be available. to those who are authorized to design install inspect maintain or. operate the electrical equipment,Author s Comment, n Proper documentation of hazardous areas assists the. designer installer and authority having jurisdiction in ensur. ing compliance with the stringent requirements contained in. Articles 501 517 of the Code, n To ensure compliance with the above requirements some. authorities having jurisdiction require drawings that indicate. hazardous classified location areas and their classification. Figure 500 3 B Other Standards Important information related to topics covered. in Chapter 5 may be found in other publications, Oil Immersion Electrical equipment immersed in a protective liquid Note 1 To ensure a proper and safe installation the authority having. jurisdiction should be familiar with the industry involved and standards of. Purged and Pressurized the National Fire Protection Association NFPA the American Petroleum. 1 Purging Class I Supplying an enclosure with a protective gas at Institute API and the International Society of Automation ISA. a sufficient positive pressure to reduce the concentration of any flam. Note 2 For further information on the classification of locations see. mable gas or vapor, Recommended Practice for the Classification of Flammable Liquids. 2 Pressurization Class I or II Supplying an enclosure with a pro Gases or Vapors and of Hazardous Classified Locations for Electri. tective gas with or without continuous flow at sufficient pressure to cal Installations in Chemical Process Areas NFPA 497. prevent the entrance of a flammable gas or vapor a combustible dust Standard for Dipping and Coating Processes Using Flammable or. or an ignitible fiber Combustible Liquids NFPA 34, Area Classification in Hazardous Classified Dust Locations.
500 3 Other Articles Flammable and Combustible Liquids Code NFPA 30. Recommended Practice for Classification of Locations of Electrical. Installations at Petroleum Facilities Classified as Class I Division 1. Except as modified in Articles 500 through 504 all installation require and Division 2 ANSI API RP 500. ments contained in Chapters 1 through 4 of the NEC apply to electrical Standard for Spray Application Using Flammable or Combustible. equipment and wiring installed in hazardous classified locations Materials NFPA 33. Liquefied Petroleum Gas Code NFPA 58, Standard for Fire Protection in Wastewater Treatment and Collection. Facilities NFPA 820, Note 3 For further information on protection against static electricity. and lightning hazards in hazardous classified locations see. Mike Holt Enterprises Inc www MikeHolt com 888 NEC CODE 632 2633 25. 500 5 Hazardous Classified Locations, Standard for the Installation of Lightning Protection Systems NFPA Author s Comment. n The same building or structure might contain any combina. Recommended Practice on Static Electricity NFPA 77. Protection Against Ignitions Arising Out of Static Lightning and Stray. tion of Class I Division 1 and 2 locations Class II Division 1. Currents API RP 2003 1998 and 2 locations and or Class III Division 1 and 2 locations. n See the definitions of Building and Structure in Article. 500 5 Classifications of Locations, B Identification of a Class I Location A Class I location is an area. where flammable gases flammable liquid produced vapors or com. Scan the QR code for a video clip of Mike explaining this. bustible liquid produced vapors may be present in quantities sufficient. topic this is a sample from the DVDs that accompany this. to produce explosive or ignitible mixtures, 1 Class I Division 1 Location A Class I Division 1 location is a.
A Classifications of Locations Locations are classified according location in which Figure 500 5. to the properties of the flammable gases flammable liquid produced. vapors combustible liquid produced vapors combustible dusts or. easily ignitable fibers flyings that may be present and the likelihood. that a flammable or combustible concentration will be present. Note To reduce expensive equipment and expensive wiring meth. ods locate as much electrical equipment as possible in an unclassified. Each room section or area is considered individually in determining. its classification Figure 500 4,Figure 500 5, 1 Ignitible concentrations of flammable gases flammable liquid. produced vapors or combustible liquid produced vapors may. exist in the course of normal operations or, 2 Ignitible concentrations of flammable gases flammable liquid. produced vapors or combustible liquids above their flash points. may exist frequently due to repair or maintenance operations or. because of leakage or,Figure 500 4, 3 Breakdown or faulty equipment releases ignitible concentrations. of flammable gases flammable liquid produced vapors or com. bustible liquid produced vapors and the electrical equipment. becomes a source of ignition, 26 Mike Holt s Illustrated Guide to Hazardous Locations based on the 2014 National Electrical Code. Hazardous Classified Locations 500 5, Note 1 Class I Division 1 locations include 2 If ignitible concentrations of flammable gases flammable.
1 Areas where volatile flammable liquids or liquefied flammable gases. liquid produced vapors or combustible liquid produced vapors. are transferred from one container to another such as at gasoline are normally prevented by positive mechanical ventilation but. storage and dispensing areas might become hazardous through failure or abnormal operation of. 2 Interiors of spray booths and areas in the vicinity of spraying and the ventilating equipment. painting operations where volatile flammable solvents are used to. 3 Areas adjacent to a Class I Division 1 location and to where. coat products with paint or plastics, flammable gases flammable liquid produced vapors or combus. 3 Locations containing open tanks or vats of volatile flammable. tible liquid produced vapors might occasionally be communicated. liquids or dip tanks for parts cleaning or other operations. unless prevented by adequate positive pressure ventilation with. Author s Comment effective safeguards against ventilation failure. n See 500 5 B 1 3 Notes 1 and 2 in the NEC for more Note 1 The quantity of flammable gases flammable liquid produced. information vapors or combustible liquid produced vapors that might escape in. case of accident the adequacy of ventilating equipment the total area. 2 Class I Division 2 Location An area where volatile flammable involved and the record of the industry with respect to explosions or. gases or combustible or flammable liquid produced vapors would fires are all factors that should be taken into consideration. become hazardous only in case of an accident or of some unusual. operating condition or under any of the following conditions Figure C Identification of a Class II Location Class II locations are those. 500 6 where the presence of combustible dust may be suspended in the. air or accumulates on electrical equipment in quantities sufficient to. ignite or explode Figure 500 7,Figure 500 6,Figure 500 7. 1 If flammable gases flammable liquid produced vapors or com. bustible liquid produced vapors are handled processed or used. but are normally confined within closed containers and the gases 1 Class II Division 1 Location A Class II Division 1 location is an. would only escape in the case of accidental rupture or breakdown area where combustible dust may exist under any of the following. or in case of abnormal operation of equipment conditions. Mike Holt Enterprises Inc www MikeHolt com 888 NEC CODE 632 2633 27. 500 6 Hazardous Classified Locations, 1 Nonconductive combustible dust is continuously or periodically. suspended in the air in sufficient quantities to produce mixtures 500 6 Material Groups. that will ignite or explode or, For purposes of testing approval and area classification various air. 2 If faulty equipment releases ignitible mixtures of dust and the. mixtures must be grouped in accordance with 500 6 A and B Figure. equipment becomes a source of ignition, 2 Class II Division 2 Location An area where combustible dust.
would become hazardous under any of the following conditions. 1 If combustible dust due to abnormal operations may be present in. the air in quantities sufficient to produce explosive or ignitible mix. 2 If combustible dust accumulation is normally insufficient to inter. fere with the normal operation of electrical equipment but where. malfunctioning of equipment may result in combustible dust being. suspended in the air or, 3 If combustible dust accumulations on in or near electrical equip. ment could be sufficient to interfere with the safe dissipation of. heat from electrical equipment or could be ignitible by abnormal. operation or failure of electrical equipment, Note 1 The quantity of combustible dust that may be present and the. adequacy of dust removal systems should be considered when deter Figure 500 8. mining the area classification, D Identification of a Class III Location A Class III location is an Author s Comment. area where easily ignitible fibers or materials producing combustible. n Refer to 500 6 A and B in the NEC to be certain that equip. flyings are handled manufactured or used and aren t likely to be sus. ment is listed for the proper group, pended in the air in quantities sufficient to produce ignitible mixtures. n The Cooper Crouse Hinds Code Digest contains a substantial. 1 Class III Division 1 Location A Class III Division 1 location is an. list of different products and their group designations It can. area where easily ignitible fibers flyings are manufactured handled or. be downloaded from www coopercrouse hinds eu en ser. vice brochures html, Note 1 Such locations usually include some parts of rayon cotton and.
and lightning hazards in hazardous classified locations see Hermetically Sealed Equipment sealed against the entrance of an external atmosphere Figure 500 3 Oil Immersion Electrical equipment immersed in a protective liquid Purged and Pressurized 1 Purging Class I Supplying an enclosure with a protective gas at

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