Installing exit signs in hazardous environments requires more than standard fixtures. In areas where flammable gases, vapors, dusts, or fibers are present, standard electrical equipment can become an ignition source. That’s why hazardous‑location exit signs use sealed housings and flame‑path designs to keep internal sparks from igniting the surrounding atmosphere. For compliant options, see our hazardous emergency lights.
Last updated: October 2025
Quick Picks
Pick Class & Division
- Class I: Gas/Vapor (e.g., propane, hydrogen).
- Div 1: Hazard present in normal operation.
- Div 2: Hazard present abnormally (leaks/maintenance).
Verify Listings
- UL 844 marking (Class/Division/Group + T‑code).
- UL 924 for egress devices (EXIT visibility & runtime).
- Ta ambient range suitable for your space.
Install Right
- Use listed sealing fittings & hubs.
- Maintain gasket & flame‑path integrity.
- Log 30‑sec monthly & 90‑min annual tests.
What Are Hazardous‑Location Exit Signs?
Often called explosion‑proof exit signs, these fixtures are engineered to contain internal arcs and flames so they don’t ignite surrounding gases or vapors. Selection starts with your area’s Class (hazard type), Division (likelihood), and Group (specific substance). Getting this right avoids red tags and protects people.
NEC Classification (Class • Division • Group)
| Class | Groups (Examples) |
|---|---|
| Class I (Gases/Vapors) | IIA (propane), IIB (ethylene), IIC (hydrogen/acetylene) |
| Class II (Dusts) | E (metal), F (coal/carbon), G (grain/wood/flour) |
| Class III (Fibers) | Ignitable fibers/flyings (no sub‑groups) |
Always confirm Division (1 or 2) and the required T‑code and Ta ambient on the nameplate.
Where Class I Div 1 Exit Signs Are Required
Use Class I Div 1 exit signs where flammable gas/vapor is present under normal operating conditions. These signs use heavy cast housings, flame paths, and gasketing to contain ignition.
Typical Div 1 Areas:
- Spray booths & solvent mixing rooms
- Digester headspaces & pump skids handling live vapors
- Offshore modules, refinery process units
Where Class I Div 2 Exit Signs Are Used
Class I Div 2 covers adjacent/abnormal‑occurrence areas where gases/vapors are not normally present but may appear during leaks, maintenance, or upsets. Equipment must still prevent ignition if a release occurs.
Div 1 vs Div 2 — At a Glance
| Criteria | Div 1 | Div 2 |
|---|---|---|
| Hazard presence | Normal/continuous | Abnormal/occasional |
| Construction | Heavier explosion‑proof housings; strict flame paths | Ignition‑safe for upset conditions; can be lighter |
| Cost/weight | Higher | Lower (model dependent) |
Nameplate & Listings (UL 844 • UL 924 • T‑Code • Ta)
- UL 844: Confirms hazardous‑location construction. Nameplate must show Class/Division/Group and T‑code.
- UL 924: Required for egress devices (EXIT visibility, transfer to battery, ~90‑minute runtime).
- T‑code & Ta: T‑code applies at a stated ambient (Ta); ensure the label covers your hottest conditions.
- Groups: Match gas family (IIA/IIB/IIC); hydrogen (IIC) is most stringent.
Temperature basics: T‑Codes for Explosion‑Proof Fixtures
Enclosures & Environment (NEMA/IP, Corrosion, Temperature)
- NEMA/IP: Where washdown, rain, or salt spray exist, specify NEMA 4X / IP66 in addition to UL 844.
- Materials/finish: Copper‑free aluminum or FRP housings; marine‑grade coatings; stainless hardware.
- Cold/hot: Consider battery heaters for cold; verify Ta for hot mezzanines or enclosures.
- Wiring: Use listed explosion‑proof sealing fittings; keep flame‑path joints pristine and bolts torqued per spec.
Compare terms: Explosion‑Proof vs Wet‑Location vs Outdoor
Common Applications & Placement Tips
- Doors & junctions: Place signs for sightlines around tanks and racks; verify visibility along the path.
- High bays & long runs: Pair exit signs with hazardous‑location emergency lights (or remote heads) to meet floor levels.
- Commissioning: Photograph nameplates; document 30‑sec and 90‑min tests for the AHJ.