Explosion-proof emergency lights are built to prevent ignition in classified atmospheres while delivering code-required egress illumination. This step-by-step guide walks electrical contractors and facility teams through the whole job—planning, mounting, conduit sealing, wiring, commissioning, and test documentation—so installs pass inspection and keep people safe.
Last updated: October 2025
Pre-Work: Safety, Classification & Submittals
- Permits & LOTO: Confirm permits, procedures, and lockout/tagout. Brief the crew on classified-area precautions and hot-work rules.
- Classification map: Identify Class (I/II/III), Division (1/2), Group (e.g., IIA/IIB/IIC; E/F/G), and required T-code.
- Scope & drawings: Add fixture locations, mounting heights, and conduit runs to as-builts; coordinate with other trades.
- Submittal packet: Include cut sheets, hazardous-location listing (UL 844), emergency listing (UL 924), intended options, and ambient (Ta) assumptions.
Background: Class/Division/Group Primer
Tools, Materials & Nameplate Checks
- Explosion-proof fittings: Listed hubs, sealing fittings, gaskets, and approved sealing compound as specified.
- Conduit & hardware: Threaded rigid conduit, anti-seize where allowed, and a calibrated torque wrench (follow OEM values and cross-pattern).
- Test gear: Multimeter, labeler for emergency circuits, lifts for aiming/testing at height; avoid megging through sensitive LED drivers/boards unless OEM permits.
- Nameplate verification: Match Class/Div/Group, T-code, and Ta to the area classification. Photograph labels for AHJ records.
Also see: T-Codes for Explosion-Proof Fixtures
Installation Steps (Mount • Seal • Wire)
- Layout & support: Mark mounting points; verify structure supports the fixture weight and aiming clearances.
- Conduit routing: Plan the run and sealing fitting locations per NEC classified-area rules. Keep flame paths and gasket surfaces clean.
- Mount the enclosure: Set gaskets, align flame-arresting joints, and tighten cover/bolts to manufacturer torque specs (even, cross-pattern).
- Make up the seals: Install listed sealing fittings and compound as directed; observe cure times; do not substitute ordinary fittings or thread sealants that compromise flame paths.
- Wiring: Land conductors per diagram; bond/ground correctly; label emergency circuits (“EM”) at panel and junctions. Avoid nicked insulation in the enclosure.
- Battery & electronics: Connect the battery per instructions (often shipped disconnected). Allow initial charge per OEM before full discharge tests.
- Aim optics: Aim adjustable heads to cover doors, stairs, and travel paths; tighten pivots without over-torque. Confirm letter sightlines if using combos.
- Housekeeping: Wipe sealing surfaces; verify no debris in flame paths; close and re-torque all fasteners. Capture nameplate photos.
Code context: Hazardous-Location Code Checklist
Commissioning & Testing (30-sec / 90-min)
- 30-sec functional: Use push-to-test or controller to confirm transfer, charge indicator, and head operation.
- 90-min discharge: Verify required illumination along the path for the full duration; measure at start and end; re-aim heads if needed.
- Documentation: Log pass/fail and corrective actions; archive cut sheets, nameplate photos, torque values, seal locations, and test forms in the commissioning packet.
- Self-diagnostics: If equipped, enable and capture status codes in your CMMS to reduce manual checks.
Inspection prep: What Inspectors Check
Placement & Photometric Tips
- Coverage first: Position to minimize shadows; prioritize egress doors, stairs, and turns.
- Mounting height: Keep heads within their effective throw; high-bay areas may need additional hazardous-location emergency lights.
- Combos vs separate: Use combos near doors; add separate hazardous-location lights for large floor areas or obstructed paths.
- Coordination: Avoid obstructions (ducts, cable trays). Re-verify after other trades finish.
Cold, Corrosive & Washdown Environments
- NEMA/IP: Choose NEMA 4X/IP66 housings and corrosion-resistant finishes in addition to UL 844.
- Ambient limits: Confirm T-codes apply at the site’s Ta; use battery heaters or shields for cold/freezer zones.
- Marine/coastal: Favor marine-grade coatings and stainless hardware; inspect gaskets more frequently.
Common Pitfalls to Avoid
- Using NEMA/IP-only gear in a classified area (no UL 844 listing).
- Wrong T-code for process chemicals or ambient temperature.
- Missing or incorrect sealing fittings; ordinary hubs used in classified conduit runs.
- Leaving debris on flame-path surfaces; under- or over-torquing cover bolts.
- Skipping 90-minute testing or failing to keep test logs for the AHJ.
Quick FAQ
Do explosion-proof lights also need UL 924?
Yes—if they provide egress illumination, they must meet emergency lighting performance (transfer and runtime) in addition to UL 844.
How close do sealing fittings need to be?
Follow the manufacturer and applicable NEC articles for your Class/Division. Use only listed sealing fittings and compound.
How soon can I test after installation?
Follow the manual—many units require an initial charge period before a full 90-minute test. Perform the 30-second test first.
This guide is informational and not a substitute for professional engineering judgment or the authority of your AHJ.