“To be beyond any existing classification has always pleased me.” — Boyd Rice
Every distiller understands that they are working with extremely explosive hazards. There is ethanol, a flammable liquid. And there is milled grain, a source of combustible dust. Despite this, when I visit distilleries, I often see areas that should be electrically classified compromised.
I don’t think it is willful disregard. I believe it is because hazardous location classification seems mysterious and perhaps not even relevant.
Hazardous location classification, or electrical classification as it is often called, is relevant in distilleries. And it doesn’t have to be mysterious.
What Is Hazardous Location Classification?
The National Electric Code (NEC), aka NFPA 70, defines hazardous locations in article 500. There are three classifications. Class I is for flammable liquids, gases, or vapors. Class II is for combustible dusts. Class III is for ignitable fibers. Unless a distillery is also operating a cotton gin, it won’t have any Class III areas. But it will have Class I areas because of the ethanol, and it will usually have Class II areas because milling grain produces combustible dust. Even if the distillery obtains its grain already milled, handling the milled grain will release combustible dust.
The fact that a flammable liquid or combustible dust is present in a distillery doesn’t mean that the entire distillery is classified as a hazardous location, however. A bottle of whiskey sitting behind the bar doesn’t mean that a tavern is a Class I hazardous location in need of an explosion-proof blender. Nor does a bag of flour on the shelf mean that a bakery is a Class II hazardous location in need of an explosion-proof dough mixer.
The reason that the NEC is concerned about hazardous locations is because electrical equipment can be an ignition source for flammable liquids or combustible dusts. It doesn’t take frayed wires or damaged heating elements, either. Ordinary electrical equipment can ignite flammable vapor clouds or combustible dust clouds, triggering destructive explosions. The electrical equipment installed in hazardous (classified) locations is sometimes called “explosion-proof”, not because it is resistant to the impact of an explosion, but because it is not likely to spark an explosion.
Divisions
Classified areas can be further divided. Division 1 refers to a location where a flammable or combustible mixture in air is normally present. “Normally” doesn’t mean “always”. It means that it is unremarkable. “Normally” also doesn’t mean “working properly.” If equipment is aways working properly, that’s great, but if a piece of equipment is prone to breaking down, then “normally” should include being in the broken-down state.
Division 2 refers to a location where a flammable or combustible mixture in air could conceivably be present, but only under rare and unusual conditions. That is, abnormally. Also, the extent of a classified location is limited. A Division 1 location doesn’t go on forever. At some point, the location is no longer classified. NEC requires that locations identified as Division 1 be isolated from areas that are “Not classified”, either by suitable barrier or a space that is Division 2.
Notice that the term is “Not classified”. Not, “Not hazardous”. Semantics, sure, but using the term “Not classified” avoids the delusion that an area is “safe”.
The Boundaries of Classified Locations
The challenge for distilleries is to establish the boundaries of their classified locations. Where do the Class I and Class II locations start, and more importantly, where do they end? And not just horizontally, but vertically? Because beyond those boundaries, ordinary electrical equipment is suitable. And ordinary electrical equipment is much less expensive that electrical equipment rated for use in classified areas.
There are three important references that guide this mapping.
When the volume of flammable liquid is less than 270 gallons (the typical volume of a tote), I am partial to the guidance in FMDS 07-32, FM Global Property Loss Prevention Data Sheet – Ignitable Liquid Operations (January 2024). FM Global makes this freely available for download. Among other things, this data sheet observes that “areas with less than 5 gal (19 L) of ignitable liquid in a single container or piece of equipment generally do not require rated electrical equipment (limited exposure).” (§2.9.1.1.A)
Otherwise, for flammable liquids, gases, and vapors, I turn to NFPA 497, Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas (2024). While it costs $157 to purchase a copy of this standard, NFPA does provide free access for viewing to anyone who registers. This volume includes a large set of classification diagrams, or “bubble drawings” as many call them, that give a number of examples of how the boundaries for Class I, Division 1 and Class I, Division 2 should be determined. It is interesting to see how the boundaries change when there is adequate ventilation. NFPA 497, by the way, defines “adequate ventilation” as six air changes per hour, 1 cfm per square foot of floor area, or anything that keeps the flammable concentration in air below 25% of the lower flammable limit (LFL). The LFL of ethanol is 3.3% by volume in air, so, 25% of that would be 0.825% by volume in air.
For defining the boundaries of Class II locations, the go-to reference is NFPA 499, Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas (2024). This standard also costs $157 to purchase, but it, too, is available for free access. Unlike Class I areas, the extent of Class II areas depends very much on housekeeping practices. That is, how well does the distillery prevent dust from accumulating. This is because while it is dust clouds that explode, piles of accumulated dust can be disturbed and become clouds.
Compromising Hazardous (Classified) Locations
It is not enough to define boundaries of hazardous locations. It is also important to assure that the equipment within those boundaries conform to the Class and Division. It is only after a distillery is built and operating that many problems occur. These problem could occur by bringing in temporary lighting that is not classified or installing permanent lighting that is not classified. Problems can result from installing electrical outlets that are not rated and then using them with ordinary electrical equipment. They can also result from running extension cords from outside the classified area and then plugging in ordinary electrical equipment.
Many types of ordinary electrical equipment can appear in classified locations after the distillery is built and operating. This includes weigh scales and other scientific instruments, most laptop computers (whether plugged in or running on batteries), radios and sound systems, coffee makers and other kitchen appliances, cell phones, and visitors’ cell phones.
Another Thing To Worry About
Large, established distilleries with technical staff are aware of all this and have procedures in place to make sure that hazardous (classified) locations are properly identified and maintained. These are not the distilleries that need to be reminded. It’s the small craft distilleries, where the owner is the head distiller and chief marketer, the purchasing agent and manager of quality control, the person responsible for compliance with TTB requirements, and a hundred other things involved in keeping a small business afloat that need to be reminded.
It is not too difficult, but maintaining a hazardous (classified) location is important in an environment where there is a potential for flammable vapor clouds and combustible dust clouds. Otherwise, an explosion can render all of those other worries moot.
