Hazardous-location egress can be covered by a single explosion-proof exit/light combo or by separate exit signs and emergency lights. This guide compares both approaches in plain English—when a combo simplifies installation, when separate fixtures deliver better coverage, and how to stay aligned with UL 844, UL 924, and your AHJ’s expectations.
Last updated: October 2025
Overview & Decision Factors
In classified spaces, you need two things: a visible EXIT legend and code‑acceptable egress illumination. Both must be hazardous‑location listed (UL 844) and meet UL 924 emergency performance where applicable. Choosing between a combo and separate fixtures comes down to:
- Coverage: Can one combo illuminate the path, or do you need additional heads across a wider area?
- Mounting height & aiming: Are heads close enough to target doors, stairs, and turns without shadows?
- Construction constraints: Do you want to minimize penetrations and devices in the classified zone?
- Inspection & maintenance: One device to test vs. separate units with flexible placement.
- Environment: Add NEMA 4X/IP66 for washdown/corrosion in addition to UL 844 hazardous‑location listing.
Related background: Explosion‑Proof vs Wet‑Location vs Outdoor
When to Use Combos (Pros & Use Cases)
- Doorways & junctions: A single unit provides EXIT identification and local illumination.
- Fewer penetrations: One enclosure can reduce conduit seals and wall/ceiling penetrations in hazardous areas.
- Simplified upkeep: One device to test (monthly/annual) and service, with fewer nameplates to document.
- Compact spaces: Ideal for small rooms, corridors, and vestibules where light throw distances are modest.
Combos shine where the egress path is short and predictable—the heads can be aimed to cover the door and immediate travel path.
When to Use Separate Fixtures (Pros & Use Cases)
- Large or high‑bay areas: Dedicated hazardous‑location emergency lights provide stronger, better‑aimed coverage.
- Flexible placement: Place exit signs for sightlines and lights for photometrics—independently.
- Layered coverage: Stairs, corners, and obstructions may require multiple heads at different points.
- Future changes: Easier to re‑aim or add heads without moving exit sign locations.
Photometrics & Placement
- Aim for uniformity: Verify foot‑candles at floor across the full 90‑minute test; re‑aim as needed.
- Mounting height: Combos near doors; separate lights to extend throw across wide bays or long corridors.
- Shadow control: Watch for ducts, tanks, and racks—add fixtures to eliminate dark zones.
Cost of Ownership: Install, Service & Testing
- Combos: Lower device count and fewer penetrations can reduce install time and sealing hardware; single battery to test/replace.
- Separate: More devices, but optimized placement may reduce the number of high‑output fixtures needed overall.
- Lift time: Plan testing routes to minimize lift moves; self‑diagnostics can reduce labor in both approaches.
- Remote heads: Consider remote‑capable units to keep batteries/electronics out of the hot zone while placing heads exactly where needed.
Upkeep: Maintenance Tips
Installation & Maintenance Considerations
- Haz‑loc listing: Confirm UL 844 Class/Division/Group and T‑code on every nameplate; UL 924 for egress performance.
- Seals & hubs: Use listed sealing fittings and compounds; keep flame‑path joints clean and bolts torqued.
- NEMA/IP: Add NEMA 4X/IP66 where washdown, rain, or salt spray is present—this is in addition to UL 844.
Code & inspections: Code Checklist • What Inspectors Check
Hybrid Layout Examples
- Door + bay: Combo above the exit door; add two hazardous‑location lights to wash a 60‑ft bay.
- Stairs + mezzanine: Combo at the stair entry; separate head at the mezzanine turn to remove shadows.
- Long corridor: Combos at each cross‑corridor door; supplemental lights every ~40–60 ft to maintain levels.
Quick Comparison Table
| Criteria | Combos | Separate Fixtures |
|---|---|---|
| Device Count | Fewer devices to install/test | More devices; targeted placement |
| Coverage | Best for doors & small spaces | Best for large/high‑bay areas |
| Installation | Fewer penetrations & seals | More flexibility on aiming |
| Maintenance | One battery/test point | Independent service per unit |
| Scalability | Limited by integrated heads | Add heads/fixtures as needed |
Quick FAQ
Do combos always replace separate lights?
No. They’re excellent at doors and tight spaces, but large areas often need additional hazardous‑location lights for uniform coverage.
Do both approaches need UL 924 & UL 844?
Yes. In classified areas, use hazardous‑location listed equipment (UL 844) and ensure emergency performance where applicable (UL 924).
What about NEMA/IP?
Use NEMA 4X/IP66 where water, washdown, or corrosion is present—this is in addition to the hazardous‑location listing.
This guide is informational and not a substitute for professional engineering judgment or the authority of your AHJ.