This guide explains how photoluminescent exit signs and tritium (self-luminous) exit signs work, where each excels, and how to keep them compliant—so you stay inspection-ready under UL 924, NFPA 101, and local code. Written in plain English for facility managers, contractors, AHJs, and building owners.
Last updated: August 2025
At-a-Glance (When to Use Each)
Photoluminescent
- “Glow-in-the-dark” pigments absorb ambient light, then re-emit in darkness.
- No wiring or batteries; needs continuous light during occupancy (~5 fc).
- Great for well-lit corridors/stairwells, schools, offices, LEED projects.
Tritium (Self-Luminous)
- Sealed tritium gas excites phosphors to glow 24/7 with no charging light.
- Ideal for persistently dark, remote, or hard-to-service areas.
- 10–20-year life; regulated recycling at end-of-life.
Quick Pick
- Choose Photoluminescent where lights stay on during occupancy.
- Choose Tritium where light isn’t guaranteed or access is difficult.
Introduction
Two energy-free options—photoluminescent and tritium (self-luminous) exit signs—offer battery-free solutions with distinct advantages. This guide explains how each works, when to use them, and what to consider for installation and code compliance.
What Are Photoluminescent Exit Signs?
Photoluminescent exit signs are glow-in-the-dark signs that absorb ambient light and emit it when it’s dark. They typically use strontium aluminate pigments to store light energy.
When mounted in well-lit areas, they remain charged and compliant with NFPA 101 and UL 924 for 90-minute visibility. Unlike electrical signs, they require no power, wiring, or batteries.
Eco bonus: No batteries; supports sustainability goals.
Explore glow-in-the-dark exit signs and confirm viewing-distance ratings (50/75/100 ft) to fit your longest sightline.
Related reading: Viewing Distance Guide (50/75/100 ft).
What Are Tritium Exit Signs?
Tritium exit signs glow continuously via radioactive tritium sealed in glass tubes; electrons excite phosphors to create visible light. They need no charging, no electricity, and no ambient light.
Ideal for total darkness or hard-to-access locations, tritium signs provide constant visibility for 10–20 years. After that, recycle through a licensed facility.
Important: Tritium is safe when sealed but must be disposed of properly. See Tritium Recycling & Disposal.
Browse self-luminous exit signs for remote or persistently dark areas.
Related reading: Do Tritium Signs Contain Radiation?
Real-World Use Cases
- Photoluminescent: Schools, offices, stairwells, LEED-focused projects with 24/7 lighting.
- Tritium: Outdoor enclosures, dark basements, remote structures, or vaults where light isn’t guaranteed.
Comparison Summary
| Feature | Photoluminescent | Tritium |
|---|---|---|
| Power Required | No | No |
| Charging Source | Ambient light (≈5 fc) | Self-contained gas |
| Visibility | 90+ minutes after outage | Always-on (10–20 yrs) |
| Maintenance | Minimal (keep area lit/clean) | Replace after lifespan |
| Eco | ✅ No batteries | ♻️ Licensed disposal |
Exit Sign Colors: Red vs Green
Both options are offered with red or green legends. Pick the hue that maximizes contrast in your space (green often excels in low light/smoke; red can pop on pale walls in bright areas). Confirm any AHJ color preference.
Code Compliance & Fire Regulations
Both types must meet UL 924 and the adopted NFPA 101/model codes. Verify local amendments before specifying.
- New York Fire Code — photoluminescent requirements in high-rises.
- California Fire Code — self-luminous acceptability/disposal.
Conclusion
Both photoluminescent and tritium exit signs provide reliable, power-free egress marking. Use photoluminescent where charging light is consistent; choose tritium where light isn’t guaranteed.
Further reading: Viewing Distance Guide (50/75/100 ft).