If you need exit signs that don’t rely on electricity yet still meet code, photoluminescent exit signs are the go-to solution. These “glow-in-the-dark” signs charge up from normal room lighting and then shine clearly during a blackout – all with no wiring, no bulbs, and no batteries. They cut energy costs to zero and simplify installation, making them popular for sustainable buildings and tricky retrofits. Whether you call them photoluminescent, non-electrical exit signs, or simply glow-in-the-dark exit signs, this guide will walk you through how they work, where to use them, and how to keep them compliant.
Last updated: October 2025
Overview: Why Photoluminescent Exit Signs?
Photoluminescent exit signs provide reliable egress marking without any power source. They absorb illumination from your building’s normal lighting (ambient light) and use that stored energy to glow brightly when the lights go out. This makes them an attractive choice to eliminate electrical wiring and batteries from exit signage. Facility managers get zero energy consumption and minimal upkeep; contractors get quick installs (no electricians or conduit); AHJs approve them when code conditions are met. In short, photoluminescent signs combine sustainability and simplicity while keeping occupants safe during an emergency.
Ideal scenario: A renovated office or historic building where running new electrical lines for exit signs is costly or unsightly. By using code-listed glow-in-the-dark exit signs, the project stays compliant and energy-efficient without altering walls for wiring.
How Photoluminescent Signs Work
Charge and glow: Photoluminescent exit signs contain phosphorescent pigments (often strontium aluminate) that store light energy. Under normal conditions, room lights continually “charge” these pigments. When the area goes dark during a power outage, the stored energy is released as a visible greenish glow, illuminating the “EXIT” legend with no bulbs or electricity. This glow is engineered to last at least 90 minutes – enough to cover the evacuation period required by safety codes – provided the sign has been receiving sufficient light beforehand.
Ambient light matters: Most photoluminescent signs need about 5 foot-candles of light on their face to fully charge. In practical terms, standard hallway or stair lighting is usually enough as people come and go. Charging is passive and continuous – there’s no switch or electronics: lights on while occupied = sign charged.
Color note: Even “red” photoluminescent exit signs rely on that greenish afterglow for nighttime visibility. The face construction (backgrounds/inks/filters) gives you red under normal light, but the nighttime emission is optimized around green because the human eye is particularly sensitive to green in low-light conditions. Properly charged, both red- and green-letter models meet UL 924 legibility at their rated viewing distance.
Pros & Cons
Advantages
- No power needed: 100% off-grid operation; zero energy cost and no wiring/battery logistics.
- Low maintenance: No lamps or electronics to fail; keep faces clean and area lighting functional.
- Fast installs: Mount like a plaque—no conduit, no panel shutdowns; ideal for retrofits/historic spaces.
- Code-compliant & safe: Listed models meet UL 924 / NFPA 101 requirements with proper charging light.
- Sustainability & TCO: Supports energy goals and reduces lifetime maintenance spend.
Limitations
- Requires adequate lighting: If faces don’t receive ~5 fc during occupancy, the glow can be undercharged.
- Viewing-distance capped: Choose 50/75/100-ft rated models to match sightlines; not as intense as LEDs.
- Not for persistently dark spaces: If light isn’t guaranteed, use tritium or an LED/battery unit.
- Still needs inspections: Verify light levels, cleanliness, and legibility during life-safety rounds.
Use Cases & Best Environments
- Office corridors & stairwells: Lights stay on during occupancy—ideal for reliable charging.
- Retrofits/historic properties: Add or replace exit signs without cutting walls for conduit.
- Sustainability-focused campuses: Eliminate energy and battery disposal at scale.
- Hard-to-wire locations: Mount anywhere with sufficient ambient lighting—no electrician.
- 24/7 facilities: Hospitals, airports, data centers—continuous lighting = continuously charged signs.
Where not to rely solely on photolum: Intermittently lit areas (storage, seldom-used rooms, auditoriums during dimmed events). In those cases, supplement or choose LED/tritium.
Color choice: Many AHJs accept both red and green legends—confirm locally. For help deciding, see Red vs Green Photoluminescent Exit Signs.
Comparisons to Tritium & LED
- Photoluminescent vs Tritium: Both are power-free. Photolum needs charging light; tritium glows continuously (no charging) but has regulatory end-of-life steps and higher costs. Use tritium where light isn’t reliable or access is difficult. For the full breakdown, see Photoluminescent vs Tritium.
- Photoluminescent vs LED: LED (AC + battery) is brighter at distance and independent of ambient light, but needs wiring and battery maintenance. Photolum shines for simplicity and TCO where ambient lighting is dependable.
Code Compliance & Requirements
- UL 924 listing: Use UL 924–listed photoluminescent exit signs (90-minute visibility, performance verified).
- NFPA 101 / IBC/IFC: Externally lit (photolum) signs are permitted when continuously illuminated during occupancy and installed per listing.
- Charging light: Plan ~5 foot-candles (~54 lux) on face under normal operation; avoid “dark by sensor” traps.
- Placement & visibility: Keep signs conspicuous with clear sightlines; use 50/75/100-ft ratings to cover the longest path segment.
- Low-level options: Photoluminescent is excellent for supplemental floor-proximity marking where required.
Visibility Range & Viewing Distance
Photoluminescent exit signs are rated for maximum viewing distance (typ. 50 ft, 75 ft, or 100 ft). Choose a rating that comfortably covers your longest sightline so evacuees always see the next EXIT as they move.
- 50-ft models: Short corridors, stair towers, turns/decision points.
- 75-ft models: Longer halls, midsize lobbies, moderate mounting heights.
- 100-ft models: Open areas, warehouses, atriums, auditoriums.
Tip: In mazy corridors, multiple 50-ft signs at intervals may serve better than a single 100-ft unit at the end. In open spaces, 100-ft units reduce fixture count. See the Viewing Distance Guide (50/75/100 ft) for choosing the right rating.
Installation & Placement
- Mounting: Wall, ceiling (top), or flag (end) mounting—no wiring required.
- Directional arrows: Apply photolum chevrons to match the egress path; be consistent at decision points.
- Lighting checks: Keep fixtures that charge the sign on emergency circuits where required; verify ~5 fc at face.
- Indoor/outdoor: Use indoor-rated units unless a model explicitly lists wet/outdoor suitability.
- Floor proximity: Use as low-level supplements where codes require them (no wiring makes these easy).
Pro tip: Measure illuminance at the sign after install and log the value for AHJ review.
Maintenance & Testing
- Keep faces clean: Dust/film reduces charging and legibility—wipe during routine rounds.
- Maintain lighting: Replace failed lamps promptly; treat area lighting as part of life-safety.
- Periodic dark checks: Do occasional lights-out drills to confirm legibility past 90 minutes.
- Recordkeeping: Note light levels and inspection dates; update if fixtures or controls change.
- End of life: No hard expiration; replace if physically degraded or persistently dim despite adequate light.
Shop Photoluminescent Models
Pick your viewing distance (50/75/100 ft), legend color (red/green), and face count (single/double). Most models include field-applied chevrons.
Visual Guide & Examples
Resources
Pillar: Non-Electrical (Wireless) Signs
Compare Power-Free Options
Color Decision Aid
FAQ
How do photoluminescent exit signs glow without electricity?
They store light from the environment and emit it in darkness. No electronics—just phosphorescent material doing the work.
Are glow-in-the-dark exit signs code compliant?
Yes—use UL 924–listed models, ensure ~5 fc on the face during occupancy, and install per listing.
How bright are photoluminescent signs vs LED?
LEDs are brighter at distance; photoluminescent signs rely on rated viewing distances (50/75/100 ft) and high contrast for legibility.
Where should I use photolum vs other types?
Use photolum where lighting is reliable and you want low maintenance; consider LED or tritium when light isn’t guaranteed or sightlines are very long.
What maintenance is required?
Keep faces clean, maintain area lighting, and do occasional dark checks. No batteries to test or replace.