You Cannot Choose These by Looking at the Fixture
Every other lighting category on this site lets you compare fixtures on output, optics, and finish. This one does not. The area classification on the drawings dictates what is permitted, the certification on the fixture either matches it or does not, and no amount of heavy construction substitutes for the right marking. A sealed but uncertified fixture from Lumera's vapor tight fixtures collection is not a substitute here, however rugged it looks.
The Classification Is Not Yours to Decide
Before selecting anything, the area has to be classified, and that determination belongs to the engineer of record, the facility, and the authority having jurisdiction. It is documented on a classification drawing, and it states which Class, which Division, and which Group applies to each space.
If a project has no classification drawing, that is the first thing to resolve rather than a gap to fill with a conservative guess. Over-specifying costs money without adding compliance, and under-specifying is a safety failure. Ask for the document.
Class, Division, and Group in Plain Terms
Three separate descriptors combine to define the requirement, and all three have to be satisfied.
Class says what kind of hazard is present. Class I covers flammable gases and vapors such as fuels and solvents. Class II covers combustible dusts, which is where grain, sugar, coal, and metal powders sit. Class III covers ignitable fibers and flyings, found in textile and woodworking operations. Lighting the unclassified parts of those same buildings is ordinary work, and Lumera's high bay lights collection covers the high-ceiling fixtures for it.
Division says how often it is present. Division 1 means the hazard exists during normal operation. Division 2 means it is only present under abnormal conditions such as a container rupture or a ventilation failure. A Division 1 fixture is permitted in a Division 2 area, and the reverse is not.
Group narrows it to the specific substance, because different materials ignite differently. Groups A through D subdivide the gases and vapors of Class I, and Groups E through G subdivide the dusts of Class II, so propane sits in Group D while grain dust sits in Group G. This is the descriptor most often dropped in conversation and it is not optional, since a fixture certified for one group is not automatically acceptable for another.
The Temperature Code Is the Most Overlooked Marking
Here is the check that gets skipped even by people who know the Class and Division system well. Every certified fixture carries a temperature code, often written as a T rating, which states the maximum surface temperature the fixture will reach in operation.
That number has to sit below the auto-ignition temperature of the substance actually present in the area. A fixture can be correctly certified for Class I Division 1 Group D and still be unsuitable if its surface runs hotter than the specific vapor in that room ignites at.
So the selection is four checks rather than three: Class, Division, Group, and temperature code against the substance. Get the ignition temperature from the safety data sheet for what the facility actually handles rather than from a general table.
What This Range Actually Contains
The eighteen fixtures here divide into two Westgate families. The round EXPR high bays cover open process floors from height, in a lower body selectable between 30W and 60W and a higher one selectable between 100W and 150W, with accessory-fitted variants listed alongside the bare fixtures. The linear EXPL high bays follow aisles, racking, and walkways at 40W, 80W, and 120W, reaching 15,600 lumens on the largest body.
All run 5000K, and both families come in standard 120-277V builds with 480V versions for facilities distributing at the higher voltage. Match the fixture certification on each product page against the marked area before anything else, and confirm the structure can carry the housing, since certified construction is heavier than the ordinary fixture it resembles.
Explosion Proof, Intrinsically Safe, and Vapor Tight
These three terms get used as if they were grades of the same thing. They are three different strategies, and only two of them are certifications for classified areas.
An explosion proof enclosure is built to contain an ignition that occurs inside it and cool the escaping gases below the point where they could ignite the surrounding atmosphere. It is heavy, and it works by containment rather than by prevention.
An intrinsically safe design goes the other way, limiting the energy in the circuit so low that it cannot produce a spark or a surface temperature capable of ignition in the first place. It is common in instrumentation and portable equipment rather than in general area lighting.
A vapor tight fixture is neither. It is sealed against water and dust ingress, which is an environmental rating with no bearing on ignition. Using a sealed but uncertified fixture in a classified area is a serious error rather than a specification shortcut.
Zones Alongside Divisions
Two systems describe the same hazards. The traditional North American approach uses Division 1 and Division 2. The international approach, now also recognized in the NEC, uses Zones, with Zone 0, 1, and 2 for gases and Zone 20, 21, and 22 for dusts.
Facilities operated by international companies, and newer installations built to international standards, increasingly specify in Zones. The systems are not a direct one-to-one translation, so if the drawing uses Zones, select against Zone-marked equipment rather than converting it in your head.
The Whole Installation Carries the Rating
This is where field failures originate. A certified fixture connected with uncertified components does not produce a compliant installation, because the classification applies to the wiring method as a system.
Conduit seals are the specific item most often missed. Classified areas require seal fittings at defined points to stop gases or dust migrating through the raceway from one area to another, and those seals have to be poured rather than simply installed. Fittings, enclosures, and every entry into the fixture have to carry appropriate ratings as well, and Lumera's electrical fittings collection covers the connectors used on those runs.
Any control or terminal equipment in the area needs an enclosure suited to the classification too, which Lumera's NEMA enclosures collection covers for the environmental side of that requirement.
Where the Classification Ends
Most facilities with a classified area also have large unclassified areas around it, and the classification drawing shows where the boundary sits. Lighting outside that boundary does not need certified fixtures, and buying them anyway is a significant and avoidable cost.
For aisles and lower back-of-house areas outside the boundary, Lumera's strip lights collection covers the utility fixtures.
Installation and Documentation
This is licensed electrician work carried out against a classification drawing, and it is inspected against that drawing rather than against general practice. Keep the fixture certification documents with the job file, because the question at inspection is which certification the fixture holds and whether it matches the marked area.
Maintenance carries the same discipline. Opening a certified enclosure and reassembling it incorrectly, or substituting a non-certified gasket or fastener, voids the protection the certification describes. Brief the maintenance crew rather than assuming the fixture is self-explanatory.
Hazardous Location Lighting FAQs
How do I know which Class and Division applies?
You do not determine it. The area classification comes from the engineer of record, the facility, and the authority having jurisdiction, and it is documented on a classification drawing. If a project has no such drawing, obtain one before selecting fixtures rather than guessing conservatively.
What is the difference between Division 1 and Division 2?
Division 1 means the hazard is present during normal operation. Division 2 means it appears only under abnormal conditions such as a rupture or ventilation failure. A Division 1 fixture may be used in a Division 2 area, but a Division 2 fixture is not acceptable in Division 1.
Why does the Group letter matter?
Because different substances ignite differently. Groups A through D subdivide Class I gases and vapors, and Groups E through G subdivide Class II dusts. A fixture certified for one group is not automatically acceptable for another, so the group has to be matched rather than assumed from the Class alone.
What is a T code and why should I check it?
It states the maximum surface temperature the fixture reaches in operation, and that has to stay below the auto-ignition temperature of the substance present. A fixture correctly certified for the Class, Division, and Group can still be unsuitable if it runs hotter than the specific material ignites at.
Is a vapor tight fixture acceptable in a classified area?
No. Vapor tight describes sealing against water and dust, which says nothing about ignition. Classified areas require fixtures certified for the specific Class, Division, and Group, and substituting a sealed but uncertified fixture is a safety failure rather than a cost saving.
Does the wiring need to be rated too?
Yes. The classification applies to the installation as a system, not just to the fixture. Seal fittings are required at defined points to stop gas or dust migrating through the raceway, and every fitting, enclosure, and entry has to carry appropriate ratings.
