Understanding Class 1 Division 1 HVAC

class 1 division 1

Understanding Class 1 Division 1 HVAC

Understanding Class 1 Division 1 HVAC

The Class 1 Division 1 (or it’s roman numeral equivalent Class i Division 1) classification defines a specific hazardous location in which ignitible flammable gases or vapors exist:


  1. Under normal operating conditions.
  2. Because of repair, maintenance or leakage.
  3. Breakdown or faulty operation of equipment which causes them to become a source of ignition. In other words, under ordinary circumstances, ignitable flammable gas or vapors exist in this space.


HVAC equipment built for Hazardous or classified environments have come to be known as “Explosion Proof.” That does not mean these air conditioners are bombproof; instead, an explosion proof air conditioner is one that was built or modified so it does not become an ignition source through arch or spark in a hazardous location where gases, dust or fibers are or may be present in combustible concentrations.

It’s the responsibility of those who understand the dangers of the
products and manufacturing environments, such as the fire marshal, plant facility engineer, or insurance underwriter, to identify the classification of a hazardous area. Many items that are generally regarded as harmless such as grains, metals, and dusts become a fire or explosion hazard when particles are less than 500 microns and dispersed in the air.

What makes Class 1 Division 1 different from other Classifications


To understand how Class 1 Div 1 units are different from other specifications, we need to know the rating system. North America specifies hazardous locations in classes, divisions, and groups. “Classes” define the general nature of the hazardous material in the surrounding atmosphere in three distinctions. Gasses (class I), Dusts (class II), and fibers (class III).



Divisions represent the probability of the hazardous material in quantities sufficient for ignition. Division 1 is a high probability in normal conditions and division 2 being a low probability in abnormal conditions.



Class 1 (Gasses) Division 1 (High probability in normal conditions). To learn more about how the explosion proof classifications visit our page “What is an Explosion Proof Air Conditioner.”

Other Posts on North American hazardous locations
Class I Division 2
Class II Division 1
Class II Division 2
Class III Division 1


From a manufacturers perspective, Class 1 Division 1 environments are the most strict, and expensive units to build. All components and equipment for Class 1 enclosures must be identified explicitly by the nameplate to work in class 1 locations.



Every element that has the potential to arch or spark must be placed in an explosion proof enclosure, this includes, contactor breakers, relays, or devices that get hot. Class 1 equipment must also not permit the exposed equipment surface to operate at a temperature over the autoignition temperature of the specified gas or vapor.



Equipment identified for Class I Division 1 locations may be installed in Class I Division 2 location of the same class, group, and temperature class, although, it’s generally not advised as the rating ads extra cost to the equipment. To avoid the expense of classified location equipment, it’s recommended to locate as much of the electrical equipment as possible to outside the classified hazardous location. Fortunately, air conditioners come in two separate sections…an Indoor (Evaporator) section and outdoor (condenser) section. These different parts of the unit can be classified differently to minimize costs. For example, If the inside of your structure is classified, a wall mounted unit would only need its evaporator (indoor) section classified because it’s the only part of the unit that will come on contact with the interior space.


Class 1 Division 1 For Sale, Rent, and Order


XP Climate Controls is a custom HVAC manufacturer that builds industrial air conditioners to exacting explosion proof and hazardous location specifications.

HVAC equipment comes in many shapes, sizes, functions, and classifications so if we don’t have your exact unit in stock, we will build it for you.

We currently stock a Class 1 Division 1 window unit or have several rental C1D1 rental units available to hold you over until we can build your unit.



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