Hazardous Location Classification Wizard
Answer a few plain-English questions about your facility, and this tool will identify the likely NEC hazardous location classification — Class, Division, and Group — for the area you're trying to specify.
Before you start
Every electrical device installed in a hazardous location (a place where flammable gas, combustible dust, or ignitable fibers might be in the air) must be rated for the specific hazard present. The rating system — defined in NEC Article 500 — uses three labels:
- Class — what type of hazard is present (gas/vapor, dust, or fiber)
- Division — how often it's present (continuously, normally, or only abnormally)
- Group — which specific material it is (acetylene, hydrogen, propane, coal dust, etc.)
This wizard walks you through determining each of those for one specific area of your facility. If your facility has multiple hazard zones, you can run it again for each.
Common questions about hazardous location classification
I don't have HAC drawings for my facility. What do I do?
A formal Hazardous Area Classification (HAC) study is required for any facility that handles flammable or combustible materials. If your facility doesn't have one — or if the existing study is outdated — you need to engage a qualified electrical engineer to perform or update it. The wizard here can give you a starting point for that conversation, but it cannot replace a real engineering study.
Why is Division 1 so much more expensive than Division 2?
Division 1 assumes the hazardous atmosphere is present under normal operating conditions. Equipment must be designed to survive ignition events inside its enclosure (flameproof construction), and motors, wiring, and seals must meet stricter standards. Division 2 assumes the hazard only exists during abnormal events, so the equipment just has to prevent normal operation from being an ignition source. The fabrication difference typically adds 20–40% to the cost of an explosion-proof unit.
What if my facility has multiple classified areas?
Most industrial facilities have multiple zones with different classifications — a pump room might be Class I, Division 1, Group D, while the adjacent control room is Class I, Division 2, Group D, and a grain storage area on the other side of the building is Class II, Division 2, Group G. Each zone needs equipment specified for its specific classification. Run this wizard separately for each area, and consult your HAC drawings to confirm the boundaries.
How accurate is this wizard?
The wizard applies the standard NEC Article 500 framework — the same logic an engineer would use in a formal classification study. Where your inputs are clear and unambiguous, the result will match what an engineer would conclude. Where inputs are ambiguous (for example, you're uncertain whether the hazard is "continuous" or just "occasionally present in normal operation"), the wizard will surface that ambiguity and recommend the more conservative classification. The tool is a starting point — final certification requires a qualified engineer and your local Authority Having Jurisdiction.
What's the difference between this and the NEC 500 ↔ Zone Converter?
This wizard determines a classification from facility conditions. The NEC 500 ↔ Zone Converter translates an existing classification between the US system (NEC 500) and the international Zone system (NEC 505 / IEC / ATEX). Use this wizard if you don't yet know your classification. Use the converter if you have one already and need it expressed in the other system.
Need help specifying equipment for your classification?
We design and modify explosion-proof air conditioning for every hazardous location classification — Class I and II, Divisions 1 and 2, all common groups. Tell us your classification and we'll send firm pricing within 24–48 hours for standard configurations.