NEC Articles 501 through 516 provide specific requirements for hazardous (classified) locations. These articles outline the standards for electrical installations in areas with potential fire or explosion hazards due to flammable gases, vapors, liquids, dusts, or fibers. Here is a summary of each article within this range:

Article 501: Class I Locations

Covers requirements for electrical equipment and wiring in Class I locations where flammable gases or vapors are present. Class I is further divided into Division 1 (normal operation conditions) and Division 2 (abnormal conditions). Key aspects include using appropriate wiring methods and protection techniques, grounding and bonding requirements, and specific equipment standards [❞].

Article 502: Class II Locations

Addresses electrical installations in Class II locations, which involve areas with combustible dust. Similar to Class I, these locations are divided into Division 1 (normal conditions) and Division 2 (abnormal conditions). It specifies requirements for dust-tight and dust-ignition-proof equipment, as well as proper wiring methods to prevent dust accumulation.

Article 503: Class III Locations

Covers installations in Class III locations, where ignitable fibers and flyings are present. This includes areas such as textile mills, woodworking plants, and similar environments. The article details the use of equipment that prevents the accumulation of ignitable fibers and ensures safe installation practices.

Article 504: Intrinsically Safe Systems

Defines the requirements for intrinsically safe systems, which are designed to operate safely in hazardous locations by limiting electrical energy to a level that cannot ignite a specific hazardous atmosphere. This article includes guidelines for equipment design, installation, and maintenance to maintain intrinsic safety.

Article 505: Zone 0, 1, and 2 Locations

Provides an alternative classification system to the Division system used in Articles 501-503. It defines Zone 0 (continuous hazard), Zone 1 (intermittent hazard), and Zone 2 (occasional hazard) for areas with flammable gases and vapors. The article includes requirements for equipment, wiring methods, and protection techniques specific to each zone.

Article 506: Zone 20, 21, and 22 Locations for Combustible Dusts and Fibers

Similar to Article 505, this article applies the Zone classification system to areas with combustible dusts and fibers. It outlines requirements for Zones 20 (continuous hazard), 21 (intermittent hazard), and 22 (occasional hazard), specifying appropriate equipment and installation practices.

Article 511: Commercial Garages, Repair, and Storage Areas

Details requirements for areas where vehicles powered by volatile flammable liquids or gases are serviced or stored. This includes provisions for proper ventilation, equipment types, and wiring methods to prevent ignition of flammable materials.

Article 513: Aircraft Hangars

Covers electrical installations in aircraft hangars where flammable or combustible liquids are present. The article provides guidelines for equipment, wiring methods, and classification of hazardous areas within hangars to ensure safety during aircraft maintenance and storage.

Article 514: Motor Fuel Dispensing Facilities

Specifies requirements for facilities where motor fuels are dispensed, including gasoline, propane, and natural gas. It includes guidelines for equipment, wiring methods, and area classifications to prevent ignition of flammable vapors during fueling operations.

Article 515: Bulk Storage Plants

Addresses installations at facilities where flammable liquids are stored or blended in bulk. This includes requirements for tank farms, transfer stations, and similar areas. The article provides standards for equipment, wiring methods, and area classifications to ensure safe handling and storage of flammable liquids.

Article 516: Spray Application, Dipping, Coating, and Printing Processes

Covers processes involving the application of flammable or combustible materials through spraying, dipping, or coating. The article outlines requirements for ventilation, equipment, and area classification to prevent ignition during these operations. It also includes provisions for handling and storing flammable liquids and powders.

For more detailed information, it is recommended to consult the NEC Handbook and additional resources provided by the NFPA. These articles ensure that hazardous locations are managed safely, minimizing the risk of fire or explosion.