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Photoluminescence Technology for Emergency Egress
For Photoluminescence technology to work, it goes through three photophysical processes. They are light absorption, energy storage, and afterglow light emissions. Photoluminescence technology use engineered phosphors to capture photons from both artificial light and natural light. This capture causes phosphors to get excited and move to a higher energy state. This state causes phosphors to get trapped in the crystal lattice which stores the energy for a long period of time. When the light source is taken away, the trapped energy is then released but in a lower energy state, which results in the light being emitted. As the crystal lattice decays, light is emitted. Strontium aluminate technology is superior to zinc sulfide technology in both longer light emissions during the afterglow processes and in the intensity of the light emitted. The light emitted is an entirely passive process which means no energy is supplied (generated) to the process and no maintenance is required, which also means that light from the photo luminescence technology will be emitted during power outages. It will light the path for egress during power outages as other forms of light fail.
Long-Persistent Luminescence, or LPL, is the term used for photoluminescent technology used for markings for emergency guidance as it falls upon the normative requirement for luminance. ISO 16069 defines the minimum requirement for luminance, which is maintained for functional emergency conditions, as 0.02 cd/m² for a minimum of 60 mins. LPL compliant materials that have guaranteed performance metrics have gone through ISO 16069 compliant testing.
Performance Metric ISO 16069 Requirement Real-World Impact
Luminance Duration ≥60 minutes visibility Sustained wayfinding in prolonged emergencies
Contrast Ratio 10:1 against background Enhanced visibility in smoke or low-contrast conditions
Charging Time <15 minutes under 50 lux Rapid reactivation after brief ambient light exposure
Markings of LPL technology that are consider for placement will guide users in the appropriate way, and markings on step edges will allow people to navigate appropriately and go up and down the stairs. LPL markings are installed under the requirement of ISO 16069, and because of that, they will provide emergency egress markings without the use of electricity.
Effectiveness of Photoluminescent Emergency Systems in the Field
Photoluminescent Systems in High Occupancy Buildings after the 2018 Edition of the IBC and NFPA 101
With the 2018 updates to the IBC and NFPA 101, officials have begun to treat photoluminescent emergency exit/path markings as an alternative to emergency exit/path lit with electric lights in code. The result has been a rapid adoption of these products in hospitals, airports, and other high occupancy buildings. Facility Safety Review (2023) reported a 57% increase in adoption of these technologies in new construction. The following factors contributed to this rapid adoption:
- Complete independence from electricity during blackouts
- 80% lower life cycle cost to maintain as compared to a wired system
- Easier to retrofit in a building with a complex architectural design
Transit hubs were the first of the newly regulated facilities to adopt these technologies, recognizing photoluminescent markings for their smoke-penetrating visibility, sustainability, and compliance with regulations confirming their use as a necessary component of modern life safety systems.
Human-Centered Standards: The ability to meet the 60 min /≥0.02 cd/m2 luminance requirement during stressful situations.
Research into the needs of evacuated persons confirms that during an emergency, the evacuee does not panic and remain oriented in the exit system if they receive a minimum luminance of 0.02 cd/m2 for the 60 min period, which has been achieved with the new strontium aluminate products. These same products were shown during controlled stress simulations to:
Performance Factor Impact on Luminance
Ambient charging (≥50 lux) 0.032-0.045 cd/m2
Sub-zero temp ≤15% reduction in output
Material aging (5+ years) Decay in output of <10% with modern alloys
Research has shown that photoluminescent markings lead to a 22% increase in evacuation speed during smoke-filled conditions compared to other systems, as the system provides continuous edge-to-edge visual guidance. Additionally, the incorporation of photoluminescent products in accordance with NFPA’s human factors design guidelines in stairwells has been shown to reduce the number of falls by 31% when the photoluminescent strip was used to clearly define the edge of the stair tread.
Photoluminescence vs. Conventional Emergency Lighting. Significant Trade-offs
Reliability Breakdown: Power Independence vs. Environmental Sensitivity (Illuminance, Temperature, Aging)
Photoluminescent systems are entirely power independent—the only ambient light exposure is an electrical connection, and no backup batteries are required. This eliminates, most, grid or battery failures responsible for 27% of conventional emergency lights discontinuing function (NFPA 2023). Nonetheless, if ambient light is not available, so is function:
Term Photoluminescent Systems Conventional Emergency Lights
Power Source Fully passive (ambient light) Grid + battery/generator dependent
Illuminance Sensitivity Requires pre-exposure to ≥25 lux for ≥60 minutes Unaffected by prior lighting conditions
Temperature Performance Performance drops 15–40% at <5°C or >40°C (per ISO 16069 test protocols) Modern component= are minimal
Aging introduces another key distinction: photoluminescent materials typically lose ~20% brightness every 5-7 years due to molecular fatigue, while well-LED maintained, emergency lights retain a stable output for 10+ years. However, if they have well maintained emergency lights, their lifecycle decisions may reflect photoluminescent units saving money. $150-$400 annually per units, in energy costs plus maintenance, but may require earlier replacement. But their reliability is dependent upon the storm, the effective evacuation guidance is based upon the level of light and ambient conditions.
FAQ
What allows some materials to glow longer than their counterparts?
These materials consist of compounds that contain strontium aluminate which are way ahead of the game in terms of long-lasting and brighter glow compared to the outdated zinc sulfide materials.
What does ISO 16069 define for the photoluminescent systems?
ISO 16069 provides guidelines for the duration of luminance, time allowed for charging, and contrast ratio for the photoluminescent systems to function as effective guidance systems for safe evacuation during emergencies.
Does the performance of photoluminescent systems degrade in certain environmental conditions?
Yes, if phenomena like prior illumination and extreme temperature changes are present, their performance can be influenced significantly.
How are photoluminescent systems different from other emergency lighting systems?
These systems are more reliable because they are not affected by power outages, are less costly to maintain, are more sensitive to environmental conditions, and prior illumination and exposure. Other systems are less reliable because they require an electrical supply.