Class 2, Division 2 Explosion Proof Air Conditioners

Class 2, Division 2 applies to locations where combustible dust is not normally in suspension in ignitable concentrations, but where dust accumulations may interfere with heat dissipation or where abnormal conditions could result in ignitable dust clouds.

Division 2 is a step down from Division 1 in severity — but it still requires explosion-proof equipment, and the requirements around surface temperature and dust accumulation are taken seriously.

Class 2 Division 2 combustible dust classification

What Is a Class 2, Division 2 Location?

Under NEC Article 500, Class 2 locations are those where combustible dust may be present. Division 2 means:

  • Locations where combustible dust is not normally in suspension in the air and normal operations do not produce hazardous dust clouds — but where dust accumulations may form on, in, or near electrical equipment
  • Locations where dust accumulations are sufficient to interfere with the safe heat dissipation from electrical equipment — and where abnormal operation might cause these accumulations to produce a hazardous condition
  • Locations adjacent to Division 1 areas where dust clouds might occasionally enter unless prevented by adequate positive-pressure ventilation

How Division 2 Differs from Division 1

In Division 1, the dust cloud is present during normal operations. In Division 2, the typical hazard is dust accumulation on surfaces — not suspended dust clouds. The concern is that accumulated dust on electrical equipment could:

  • Insulate the equipment and cause overheating
  • Be ignited by hot surfaces, sparks, or arcing
  • Under abnormal conditions (equipment failure, housekeeping interruption), become suspended in ignitable concentrations

Common Class 2, Division 2 Environments

  • Grain storage facilities — areas outside active transfer points but where dust settles
  • Flour and feed mills — packaging areas, storage rooms, and adjacent spaces
  • Pharmaceutical plants — areas near but not within active powder processing
  • Coal storage — areas away from active conveying or crushing operations
  • Plastics manufacturing — grinding and cutting areas where dust settles on surfaces
  • Sugar facilities — storage and packaging areas
  • Woodworking — areas adjacent to Division 1 sawdust-generating operations

Class 2 Groups: E, F, and G

As with Class 2, Division 1, the group is determined by the type of combustible dust present.

Group E — Metal Dusts (Electrically Conductive)

Group E covers electrically conductive metal dusts. Even in Division 2, the electrical conductivity of Group E dusts means dust accumulation inside electrical enclosures poses a shorting and tracking risk — not just an ignition risk. Equipment requirements for Group E in Division 2 are closely aligned with Division 1 requirements.

Common substances: Aluminum, magnesium, and other reactive metal dusts Common industries: Aluminum production, metalworking, some mining operations

Group F — Carbon Dusts

Group F covers carbonaceous dusts with significant volatile content. These include some materials with higher auto-ignition temperatures than Class 1 materials, but the accumulation risk remains significant.

Common substances: Carbon black, charcoal, coal dust, coke dust Common industries: Coal storage, carbon processing, activated carbon facilities

Group G — Grain, Flour, Plastic, Chemical, and Other Non-Conductive Dusts

Group G is the most commonly encountered Class 2 classification. These non-conductive combustible dusts accumulate on surfaces and can be ignited if equipment surfaces are hot enough or if an ignition source is present.

Common substances: Flour, starch, grain dust, sugar, wood, plastics, and similar materials Common industries: Grain elevators, flour mills, feed mills, food processing, pharmaceutical manufacturing, plastics processing

Why Division 2 Still Requires Explosion-Proof Equipment

A common misconception is that Division 2 means you can use standard equipment. That’s not correct.

While Division 2 allows some equipment types that are not permitted in Division 1 — for example, equipment with components that make or break current only inside hermetically sealed chambers — the fundamental requirement for dust-tight enclosures and appropriate surface temperature ratings still applies.

For air conditioning equipment specifically:

  • Enclosures must prevent dust accumulation from interfering with heat dissipation
  • Motor enclosures must prevent dust ingestion (TEFC or TENV)
  • Surface temperatures must remain below the auto-ignition temperature of the dust
  • All wiring must be in conduit with sealed fittings

The difference in Division 2 is primarily that some additional equipment types are available — not that standard commercial equipment is acceptable.

Class 2, Division 2 Air Conditioner Modifications

We modify standard air conditioning units for Class 2, Division 2 service:

  • Motor replacement with TEFC or TENV motors rated for Groups E, F, or G as required
  • Enclosure hardening to prevent dust accumulation from blocking airflow and causing overheating
  • Surface temperature management to ensure external surfaces remain below dust auto-ignition temperatures
  • Conduit installation with appropriate sealed fittings
  • Optional coil coating for corrosive environments
  • Documentation for compliance records

Pricing and Quotes

Class 2 modifications are quoted case by case based on group, unit size, and scope of work.

Call (844) 925-5668 — we typically return quotes within 24–48 hours.

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