Photoluminescent (glow-in-the-dark) exit signs can be fully code-compliant when installed correctly. This guide distills the essentials of UL 924, NFPA 101, IBC/IFC, and OSHA for non-electrical EXIT signage—covering listing & labeling, the 90-minute visibility rule, the 5 fc ambient-light requirement, placement/spacing, and what AHJs expect at plan review and inspection.
Last updated: October 2025
Overview: When Photolum Makes Sense
Photoluminescent (PL) exit signs absorb normal room lighting and re-emit it during a blackout. They cut energy to zero, simplify installation (no wiring, no batteries), and still meet egress rules when properly specified and installed. They’re a strong fit for corridors, stair towers, offices, schools, and retrofits—spaces that are consistently lit while occupied. If a location is routinely dim or dark with occupants present, consider LED (AC + battery) or, where appropriate, self-luminous tritium instead.
New to PL signs? See our Photoluminescent Exit Signs 101 for fundamentals and selection basics.
What Qualifies as a Photoluminescent Exit Sign
A compliant PL sign is a listed EXIT device whose legend remains legible for the required duration without an internal light source. It relies on a continuous external light source during occupancy to “charge” the face. Packaging/labels indicate UL 924 listing, legend size/format, and a rated viewing distance (e.g., 50/75/100 ft). If those items are absent, it isn’t an acceptable exit sign—regardless of marketing claims.
UL 924 Listing & Labeling (Non-Negotiable)
UL 924 is the acceptance gate for exit signs in most U.S. jurisdictions. For photoluminescent models, the UL 924 mark certifies minimum luminance, decay performance, legend format (e.g., 6″ letters, 3/4″ stroke), and visibility at a labeled distance after extended darkness. Inspectors typically request evidence of listing—keep the cut sheet and UL label handy in your submittal set and facility file.
- Legend format: Standard 6″ letters with 3/4″ stroke (unless your AHJ approves an alternate listed format).
- Labeled viewing distance: Readable at its rating after 90 minutes of darkness (see Visibility).
- No listing, no go: Decorative “glow” plaques/stickers are not substitutes for a UL 924 exit sign.
NFPA 101 Cross-Walk (Life Safety Code)
NFPA 101 requires exit signs to be listed and remain visible during emergency conditions. It permits photoluminescent (externally illuminated) exit signs if they are lit whenever the building is occupied and installed per their listing. The performance intent is simple: occupants must always be able to identify the way out—even after normal lighting fails.
- Continuous illumination: Charging light on during occupancy per the listing.
- Legend & placement: Conspicuous along egress; arrows at turns.
- 90 minutes: Visibility maintained for ≥ 1.5 hours after power loss.
IBC/IFC & OSHA—How They Interlock
IBC/IFC mirror NFPA’s approach: exit signs can be internally illuminated or externally illuminated (photoluminescent) if they are continuously lit during occupancy and listed to UL 924. OSHA recognizes compliance through the adopted life-safety/building codes—meet UL 924 and the jurisdiction’s code version, and you satisfy OSHA expectations.
90-Minute Visibility & Viewing Distance Ratings
Every exit sign must remain legible for ≥ 90 minutes after loss of normal power. PL signs do this via stored luminescence. Because brightness decays over time, the labeled viewing distance (50/75/100 ft) becomes your design guardrail—space signs so the next EXIT is visible before occupants exceed the prior sign’s rating.
- 50 ft: Short corridors, stair towers, frequent turns/decision points.
- 75 ft: Longer halls, midsize lobbies, moderate mounting heights.
- 100 ft: Open areas, warehouses, atriums, auditoriums.
Tip: In a 120-ft hallway, either place two 50-ft signs (staggered) or one 100-ft model with clear sightlines. Around bends, stagger smaller ratings rather than rely on one long-range unit.
Ambient Light Requirement (~5 fc on the Face)
PL signs must be continually illuminated during occupancy. Most listings call for ~5 foot-candles (≈ 54 lux) on the sign face. This is the single biggest success factor: no charging light = no usable glow.
- Design & verify: Use a light meter to confirm ≥ 5 fc after install; document readings in your life-safety file.
- Controls: Avoid “dark by sensor” traps—ensure controls never leave a PL sign unlit while occupied.
- Emergency feeds: Where required, serve charging fixtures from emergency power for prolonged events.
- Clean faces: Dust/film reduce charging; include periodic wipe-downs in rounds.
Placement, Spacing & Arrow Conventions
- Height: Follow listing/code (typ. bottom ≥ 80″ AFF) unless a listed low-level sign is permitted.
- Sightlines: Ensure the next EXIT is visible before passing the rated distance of the previous sign.
- Turns: Apply chevrons at decision points; avoid recesses/soffits that starve the face of charging light.
- Two-way approaches: Use double-face or back-to-back mounting.
- Doors & discharge: Mark above exits and along exit access to the public way.
Color & Contrast (Red vs Green, Backgrounds)
Many jurisdictions accept either red or green legends; some require one color—confirm with your AHJ. Maintain strong contrast with adjacent finishes (avoid near-match backgrounds). If you’re unsure about color, match existing signage for route consistency.
Low-Level / Floor-Proximity Use
Some occupancies require low-level exit signs (e.g., certain high-rise stair towers). PL is excellent here because no wiring is needed at the base of the wall. Verify the model’s listing for floor-proximity use and mount per manufacturer instructions.
Plan Review & AHJ Submittals—What to Show
- UL 924 proof: Include the cut sheet showing UL 924 listing and labeled viewing distance.
- Lighting note: State “≥ 5 fc maintained on PL sign faces during occupancy” and identify charging fixtures.
- Locations & arrows: Show each sign and chevrons; verify spacing against viewing-distance ratings.
- Local amendments: Address color mandates, low-level signage, pictograms, or high-rise provisions.
- Field checks: Retain light-meter readings and periodic “lights-out” verification in your life-safety log.
Operations: Documentation, Inspections & Maintenance
PL signs have no batteries to test—but they’re still part of your life-safety program. Keep a simple record of face illuminance (≥ 5 fc), cleaning intervals, and periodic “lights-out” checks confirming legibility at the rated distance after a simulated outage. If a sign underperforms, verify nearby fixtures first (lamp out? dimmed controls?) before suspecting the sign.
- Cleaning: Wipe faces on a routine schedule; avoid coatings/decals that block charging.
- Relighting: If lighting levels change (fixture swap, controls update), re-verify foot-candles at the sign.
- Replacement: PL signs have long service life; replace if physically degraded or persistently dim despite adequate charging light.
Quick Compliance Checklists
Design / Submittal
- UL 924–listed photoluminescent models specified; labels retained on drawings and cut sheets.
- Viewing distance (50/75/100 ft) matches longest sightline between signs.
- Lighting plan notes ≥ 5 fc on sign faces during occupancy; identify charging fixtures.
- All sign locations and chevrons shown at decision points; low-level units noted (if required).
Installation
- Signs mounted with clear sightlines; no alcove/soffit shadowing the face.
- Double-face or back-to-back mounting for two-way approaches.
- Arrows applied to match actual egress turns; contrast with adjacent finishes verified.
Operations
- Light-meter readings on file (≥ 5 fc at each face); periodic re-checks after lighting changes.
- Faces kept clean; no opacity-adding stickers/films; “lights-out” checks logged.
- Deficiencies corrected (relamp, controls, relocation) to maintain listing conditions.
FAQ
Are glow-in-the-dark exit signs really code-compliant?
Yes—if they are UL 924–listed, installed with continuous charging light during occupancy, and spaced to respect the rated viewing distance. That’s the package inspectors look for.
Do I still need emergency power if I use photoluminescent signs?
You still need code-required emergency lighting, but the signs themselves do not need power. Provide reliable charging light on the faces during occupancy per the sign’s listing.
How do inspectors verify compliance?
Common asks: UL 924 cut sheet/label, face illuminance evidence (≥ 5 fc), locations/chevrons on plans, and a quick “lights-out” check to confirm legibility at the rated distance.
When should I use LED or tritium instead?
Use LED where you need high brightness at long distances or the area is sometimes occupied while dark; use tritium where charging light isn’t guaranteed and wiring is impractical. Otherwise, PL is often the simplest, lowest-TCO option.