Explanation of Hazardous Locations – Class 1 Div 1, Groups A, B, C, and D

My first job out of the Navy was in industrial & chemical pump repair. Oftentimes, the customer would remove the pump from its installation and send it in for us to fix. Other times, we’d go out to their facility if it was an exceptionally large pump and/or if seeing what it was doing (or not doing) while it was running was beneficial. Sometimes the pump was located in an area that was designated as explosion proof, or classified. There were different precautions we’d need to take, depending on what the particular hazard (or potential for a hazard) was. More often than not, that meant that we had to observe some VERY basic safety rules…no open flame was a biggie…but occasionally, we’d have to take apart a pump in an area that required us to use non-sparking tools. One time, I actually had to attach a grounding strap to my wrist, because even a spark from a static charge could have been bad news.

Electrical products that are operated in such areas have to meet certain requirements, or classifications.  In the United States, the National Electrical Code (NEC) defines these areas in a system of Classes, Divisions, and Groups, depending on the nature of the material that presents the hazard (Class), whether it normally exists or if it’s just possible in abnormal situations (Division), and the specific type of the subject material (Group). Today’s blog is all about what would classify an area as Class I, Division 1, and which Group the specific hazardous material falls under.

A Class I location means that the hazard is a flammable gas or vapor which is present in the area, in a high enough concentration to be considered ignitable. These were the locations that we were required to use non-sparking tools in, and for good reason. Some examples of Class I locations are:

  • Petroleum refineries
  • Gasoline storage or dispensing areas
  • Aircraft hangars and fueling stations
  • Spray finishing rooms or booths

Division 1 means that the flammable gas or vapor that makes the area a Class I location is present in the atmosphere during normal operating conditions and/or when the gas or vapor is released to the atmosphere during maintenance or repair work. These gases & vapors aren’t present in ALL areas of the above listed Class I examples during normal operation, so only the areas where they ARE present during normal operations would be defined as Division 1. For example:

  • Areas where a gasoline tank (in a refinery or gasoline storage/dispensing station, for example) is vented to the atmosphere are Class I Division 1, because the vapor coming out of the vent is doing so by design…you can’t pump a liquid into a non-vented tank.
  • Only the parts of an aircraft hangar where fuel is actually being handled are Division 1. That wouldn’t necessarily apply to a stock or communications room in the hangar, though.
  • The interior of a paint booth is Division 1 because the spray is volatile, as is the immediate vicinity adjacent to an open spray booth.

Class I designation is further divided into four Groups, based on two specific characteristics of the gas or vapor that basically express how easy it is to cause (or how hard it is to prevent) an explosive hazard:

  • Maximum Experimental Safe Gap (MESG) – The gas is put in the interior chamber of a vessel with an adjustable gap that leads to the outer chamber. MESG is the largest gap between the chambers that will prevent ignition of the gas.
  • Minimum Igniting Current (MIC) ratio. This is the ratio of the minimum current from an inductive spark required to ignite the gas, divided by the minimum current from an inductive spark that will ignite methane under the same conditions.
  • Group A: Acetylene
    • MESG = 0.25 mm
    • MIC ratio = 0.017
  • Group B: Hydrogen, butadiene, ethylene oxide, propylene oxide, and acrolein
    • MESG <0.45mm (except acetylene)
    • MIC ratio <0.4 (except acetylene)
  • Group C: Ethylene, cyclopropane and ethyl ether
    • MESG = 0.45mm to 0.75mm
    • MIC ratio = 0.4 – 0.8
  • Group D: Acetone, ammonia, benzene, butane, ethanol, gasoline, hexane, methane, methanol, methane, naphtha, natural gas, propane and toluene
    • MESG >0.75mm
    • MIC ratio >0.8

EXAIR HazLoc Cabinet Cooler Systems are engineered and approved for use on electrical enclosures in these areas, as well as Class II and Class III. Our ATEX Cabinet Cooler Systems are compliant with the European Union’s ATEX Directive (Zones 2 and 22).

Both the HazLoc (left) and ATEX (right) Cabinet Cooler Systems are available from stock in NEMA 4 and NEMA 4X ratings.

Wherever the panel you need cooling for is located, we’ve very likely got a reliable and safe solution. If you’d like to find out more, give me a call.

Russ Bowman, CCASS

Application Engineer
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Choosing The Right Cabinet Cooler System

EXAIR Cabinet Cooler Systems provide heat protection for electrical enclosures, especially those in more “aggressive” environments. They’re durable & reliable, and unlike other devices (panel A/C, I’m looking at you), they’re impervious to environmental conditions and contamination…which they’ll also protect your electrical enclosures from. My colleague Jordan Shouse did a fabulous job of explaining how they work in a blog entitled (appropriately enough) “EXAIR Cabinet Cooler Systems – How Do they Work?” so I’ll get right to point of today’s blog, which is the selection process.

First, we need to calculate the heat load. If it’s for cooling a panel currently in operation, you need three things:

You’ll use the thermometer to “take the panel’s temperature”. See, we calculate the internal heat load (that’s the amount of heat generated by the components inside the panel) by using the difference between the internal air temperature, and the external air temperature. Since we’re essentially air conditioning the panel, it’s important to get air temperatures (from a thermometer) rather than surface temperatures (from a heat gun or similar instrument).

You won’t need the thermometer for this, but we’ll also need to know the maximum ambient temperature in the area where the panel is installed. This is to calculate the external heat load, and also determine if a High Temperature model is needed (more on that in a minute).

The tape measure is to get the length, width, and height of the panel. We also need to calculate the heat transfer surface area. A ruler or yardstick would work as well.

If there’s something cooling the panel already – whether it’s panel A/C, fan circulation of environmental air through the panel, etc. – we’ll need to know about that too, because you’ll be removing that for optimal performance of the Cabinet Cooler System.

Once you have all that, you can enter the data (and a few other things, which I’ll get to momentarily) at the above link to the Sizing Guide. If you’re a DIY type person (or control freak…no judgment from ME on that), there’s also a link there to our new Cabinet Cooler System Calculator. You can also print a copy of the Sizing Guide and email it or fax it in. Or…you can call me with the data. It only takes a minute to do the calculation, and we do it over the phone all the time.

Next, we need to know about the environment in which it’ll be installed, so we can specify certain parameters like:

  • NEMA rating. We make Cabinet Coolers for three distinct ratings, depending on the environment in which they’ll be installed.
    • NEMA 12 means it’s dust tight & oil tight, indoor duty. If no liquids or corrosives are present, this is probably what you’re looking for.
    • NEMA 4 means it’s dust tight, oil tight, splash resistant, indoor/outdoor duty. These have a low pressure relief valve for the Vortex Tube’s hot flow, and the exhaust from the panel, to maintain the splash resistant integrity of the panel.
    • NEMA 4X systems meet all requirements for a NEMA 4 rating, and are made of Type 303 Stainless Steel for corrosion resistance. We also make them in Type 316 Stainless Steel for higher levels of corrosion resistance, which is oftentimes specified in food and pharmaceutical environments.
  • Ambient temperature. If they’re going to be installed in areas where the temperature can exceed 125°F, there are some internal components made of plastic & buna that aren’t rated for that. In those cases, we specify a High Temperature Cabinet Cooler, where we replace those with components made of brass and Viton, respectively. Those are good for up to 200°F environments.
  • Atmospheric contaminants. All of our systems are, at a minimum, oil & dust tight per the above NEMA ratings. If a panel isn’t completely sealed – maybe there’s a cable bundle going through a loose grommet, or the door/front panel isn’t gasketed – then airborne stuff that you ideally want to keep away from sensitive electrical/electronic gear can still make it in. For those, we have two options:
    • Continuous operating systems will provide cold air flow for cooling and positive purge as long as compressed air is flowing to the Cabinet Cooler. That’ll keep the bad stuff out, but it’ll also get your panel colder than it needs to be, and you’ll pay for that with the increased cost of the full rated compressed air flow.
    • Non-Hazardous Purge systems allow Thermostat Control to turn off the compressed air flow when it’s not needed, and still pass 1 SCFM through the Cabinet Cooler (instead of full flow) when the internal temperature is at or below the Thermostat setpoint. These cost considerably less to run than Continuous Operation systems.
  • Thermostat Control. Agencies like Compressed Air Best Practices and the Compressed Air Challenge include panel cooling on their list of inappropriate uses of compressed air – EXCEPT when they’re thermostat controlled. EXAIR uses Solenoid Valves operated by bimetallic thermoswitches with superior response times, so the Cabinet Cooler doesn’t continue running once it’s cooled the panel to the setpoint temperature, and (more importantly) comes on as soon as the temperature rises above that setpoint to further guard against heat damage. They’re available in 120VAC, 240VAC, and 24VDC options.
The Thermostat’s (left) leads are spliced into the Solenoid Valve’s (bottom right) ‘hot’ lead, which essentially makes it an automatic temperature controlled ‘on/off’ switch for the Cabinet Cooler System. NEMA 4/4X versions include mounting hardware (top right).
  • Thermostat Control part 2. There are situations where the ability to change the regulated temperature is desirable. While the Thermostat’s setpoint can be changed, EXAIR’s ETC Electronic Temperature Control allows you to change it, at the push of a button. It also gives a continuous display of the actual temperature inside the panel that can alert operators to a potential overheating situation before the alarms start going off, or, if there are no alrms, before all those expensive electronic devices start to fry.
ETC Electronic Temperature Control can be used in a wide variety of applications.

EXAIR’s Cabinet Cooler Promotion also started June 1st if you’re interested in purchasing one for your process. For a limited time, you can order any of EXAIR’s Cabinet Cooler® Systems and get a FREE AC Sensor with purchase! Check it out here.

If you’d like to discuss the ease at which you can provide safe, effective, and reliable heat protection for electrical panels in almost any environment, give me a call.

Russ Bowman, CCASS

Application Engineer
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Hazardous Location Cabinet Coolers

Last year was a big year for EXAIR’s Cabinet Cooling product line, in November  we launched our first Hazardous Location Cabinet CoolersEXAIR has always been a leading supplier in compressed air-based Cabinet Coolers, now we have expanded on that to work in the most high-risk conditions.

When a Hazardous Location Cabinet Cooler is used in conjunction with a purge system, they will keep electrical equipment at the desired operating temperature to protect and lengthen the lifetime of pricey controls and power supplies.

Hazardous Location Cabinet Cooler


Electrical equipment can cause explosions in certain atmospheres. Equipment used in areas where explosive concentrations of dusts or vapors may exist must be equipped with special wiring and other electrical components for safety purposes. Hazardous (classified) locations such as these might exist in aircraft hangars, gasoline stations, paint-finishing locations or grain bins. EXAIR’s Hazardous Location Cabinet Coolers have been approved and tested by UL for use in the following areas:

UL Approved and Tested

Class I Div 1&2 – Groups A, B, C, and D

  • Class I Areas refer to the presence of flammable gases or vapors in quantities sufficient to produce explosive or ignitable mixtures. Class I Div 1 will have ignitable concentrations of flammable gases present during the course of normal operations. This is level of approval is one that differentiates the EXAIR Hazardous Location Cabinet Coolers from much of the competition. Class 1 Div 2 areas will have flammable gasses or vapors present only in the event of an accident or during unusual operating conditions.

Class II Div 1&2 – Groups E, F, and G

  • Class II areas are locations in which combustible dust may exist. The end user shall avoid installation of the device in a Class II environment where dust may be readily disturbed from the exhausts of the Hazardous Location Cabinet Cooler. Any dust formed in the vicinity of the cooler must be cleaned regularly.

Class III

  • Class III areas are locations that will have ignitable fibers or flyings present. This is common within the textile industry.

The Cabinet Cooler also carries a temperature rating of T3C, meaning it cannot be installed near any materials that could auto-ignite at temperatures in excess of 320°F.

The Hazardous Location Cabinet Cooler is available in (8) different cooling capacities ranging from 1,000 Btu/hr – 5,600 Btu/hr. The Cabinet Cooler is the best solution for protecting your sensitive electronics from heat, dirt, and moisture. With Nema 4/4X systems available, the Hazardous Location Cabinet Coolers will keep the cabinet cool without compromising the integrity of the enclosure.

If you’ve got an electrical cabinet installed within a hazardous location, fill out the Cabinet Cooler Sizing Guide and allow an EXAIR Application Engineer to determine the most suitable model for you.

Jordan Shouse
Application Engineer
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UL Classified Certification for HazLoc Cabinet Coolers

Although history only records back so far, I am certain (based on my experiences with sharp and heavy objects) that humans have been injuring themselves with tools, and the stuff they make with them, since the beginning of time.  In fact, recorded history DOES bear this out…the famous Code of Hammurabi (circa 1750 B.C.) set specific amounts of compensation for specific injuries, as did laws from all over the ancient world, from the empires of Rome to China.  Since then, we’ve come a long way in regulating safety not only for the worker in the workplace, but in public places, homes, and workplaces where manufactured products are used.

UL LLC (or Underwriters Laboratories, as they were known throughout the 20th Century) is a safety consulting & certification company founded in 1894 by an electrical engineer named William Henry Merrill.  A year earlier, an insurance company hired Merrill to perform a risk assessment and investigation of new potential clients…George Westinghouse and Nikola Tesla, the proprietors of the Palace of Electricity at the 1893 Chicago World’s Fair.  It was this experience that made him realize the potential for such an agency to test and set standards for product safety at the dawn of a new age of technology development.  And 120 years on, the benefits in safety & protection have been proven many times over.

If a product or device carries one of these markings, it’s been evaluated for safety by top professionals in the field.

One of the more critical accreditations that a manufacturer can receive for a product is the UL Classified Mark.  This differs from other markings (like the ones shown above for Certified, Listed, or Recognized) in that Classification means that samples of the product were tested & evaluated with respect to certain properties of the product.

EXAIR’s new Hazardous Location Cabinet Cooler Systems bear the UL Classified Mark.  This means they meet the stringent UL requirements for installation on purged electrical enclosures in specific classified areas:

  • Class I Div 1, Groups A, B, C and D
  • Class II Div 1, Groups E, F and G
  • Class III

EXAIR Hazardous Location Cabinet Cooler Systems maintain NEMA 4/4X Integrity and are CE Compliant.

When choosing products for use in classified areas, it’s critical to ensure safety through compliance, and the HazLoc Cabinet Cooler Systems allow you to do that, with simplicity and reliability.  If you’d like to discuss an enclosure cooling application, in or out of a classified area, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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