Info

Protection concepts – NEC and CEC

Electrical equipment installed in hazardous locations must comply with the National Electrical Code (NEC) in the United States and the Canadian Electrical Code (CEC) in Canada.

These codes define approved protection concepts intended to prevent the ignition of flammable gases, vapors, combustible dusts, or fibers when electrical equipment is installed or operated in hazardous environments.

The protection methods recognized by the NEC and CEC are based on specific fundamental safety principles, such as:

  • Containing an internal ignition
  • Preventing arcs, sparks, or hot surfaces
  • Limiting available energy to non-ignition levels
  • Isolating or sealing ignition-capable components

The tables referenced in this section summarize the recognized protection methods and show how they are applied under both NEC and CEC requirements.

The information is structured to allow quick cross-referencing between Class and Division systems, enabling engineers, inspectors, and specifiers to determine:

  • Which protection concepts are permitted for a given hazardous location
  • Whether a method is acceptable under U.S. and Canadian codes
  • How protection concepts align across different classification systems

This matrix-style approach simplifies code compliance review and supports accurate specification of equipment for hazardous location installations.

Electrical equipment for flammable gases, vapours and mist
US code CAN code Type of protection Basic concept of protection Class I Div Class I Zone US Standard CA Standard
1 2 0 1 2
AEx e Ex e Increased safety No arcs, sparks or hot surfaces        • • ISA 60079-7 CSA E60079-7
(NI) (NI) Non-incendive      •     ISA 12.12.01 / FM 3611 C22.2 No. 213
AEx nA Ex nA Non-sparking   •       ISA 60079-15 CSA E60079-15
(XP) (XP) Explosion proof Contain the explosion and • •       UL 1203 / FM 3615 C22.2 No. 30
AEx d Ex d Flame proof extinguish the flame       • • ISA 60079-1 / UL 1203 / FM 3615 CSA 60079-1
AEx q Ex q Powder filled         • • ISA 60079-5 CSA E60079-5
AEx nC Ex nC Enclosed break           • ISA 60079-15 CSA E60079-15
(IS) (IS) Intrinsic safety Limit energy of sparks and surface temperature • •       UL 913 / FM 3610 22.3 No. 157
AEx ia EX ia     • • • ISA 60079-11 / FM 3616 CSA E60079-11
AEx ib EX ib       • • ISA 60079-15 CSA E60079-15
AEx nL EX nL Limited energy         • ISA 60079-15 CSA E60079-11
Type X Type X Pressurised Keep flammable gas out • •       NFPA 496 (FM 3620) NFPA 496
Type Y Type Y • •      
Type Z Type Z   •      
AEx px Ex px       • • ISA 60079-2 CSA E60079-2
AEx py Ex py       • •
AEx pz Ex pz         •
AEx nR Ex nR Restricted breathing         • ISA 60079-15 CSA E60079-15
AEx m Ex m Encapsulated       • • ISA 60079-18 CSA E60079-18
AEx ma N/A     • • • N/A
AEx mb       • •
AEx o Ex o Oil immersion       • • ISA 60079-6 CSA E60079-6

 

Electrical equipment for combustible dust
US code CAN code Type of protection Basic concept of Class II Div C III Div Class II Zone US Standard CA Standard
protection 1 2 0 20 21 22
(DIP) (DIP) Dust ignition protection Keep combustible dust out • • •       UL 1203 / FM 3616 CSA C22.2 No. 25
(NI) (NI) Dust protected   • •       ISA 12.12.01 / FM 3611 CSA C22.2 No. 25
AEx ta Ex ta Protection by enclosure       • • • ISA 60079-31 CSA C22.2 No. 60079-31
AEx tb Ex tb         • •
AEx tc Ex tc           •
N/A N/A Fibre & flying protection     •       UL 1203 / ISA 12.12.01 CSA C22.2 No. 25
AEx maD N/A Encapsulation       • • • ISA 60079-18 N/A
AEx mbD         • •
(PX) (PX) Pressurisation • • •       NFPA 496 (FM 3620) NFPA 496
(PY) (PY) • • •      
(PZ) (PZ)   • •      
AEx pD N/A       •     ISA 61241-2 N/A
(IS) (IS) Intrinsic safety Limit energy of sparks • • •       UL 913 / FM 3610 CSA C22.2 No. 157
AEx iaD N/A and surface temperature       • • • ISA 60079-11 N/A
AEx ibD           • •