Classified Area Requirements: In general, electrical equipment used in a Division 1 location, and switches or other make-break contact devices used in a Class I location, are required to be marked for use in the installed location. However, electrical equipment used in a Division 2 area is not always required to comply with this marking requirement, allowing for use of general-purpose equipment.

General Use Equipment – US NEC: Part III of Articles 501, 502, and 503 of the U.S. National Electric Code (NEC) include specific allowances for general-purpose equipment that is permitted to be located in Classified Areas. These allowances are primarily for windings (without contacts or brushes) and resistors (i.e. heaters) for Class I locations. Class II locations permit the use of some switching devices when installed in dust-tight enclosures.

Division 2 Considerations: Because Division 2 areas typically only present a flammable atmosphere in the event of an accident or unusual operating condition, consideration for explosion protection is usually only required with electrical equipment operating normally. If the equipment does not contain any normally arcing or sparking parts, considerations for spark ignition may not even be needed.

Thermal Considerations: One big caveat is that although the NEC permits the use of general-purpose equipment in some cases, it does not exempt this equipment from complying with section 500.8 of the NEC. This section requires all equipment to be suitable for the thermal ignition properties of the flammable material (gas, vapor, etc.). So, regardless of the type of equipment, consideration for thermal ignition is always required. This means that the temperature of any surface exposed to the flammable material must be known to be less than the auto-ignition temperature of the flammable material.

In normal operation, this may not be difficult for some equipment. However, special consideration is required for heaters in Class I locations. Surface temperatures of heaters are not permitted to exceed 80% of the auto-ignition temperature.

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