When the power fails, two systems keep a building safe to leave: emergency lighting that keeps the exit path visible, and exit signs that show people where to go. Both are life safety equipment, and both are inspected. This guide covers what the codes actually require, so you can spec, install, and maintain them with confidence.
The rules come from the NFPA 101 Life Safety Code and the model building and fire codes (the IBC and IFC), which California adopts and amends as the California Building Code and California Fire Code under Title 24, Parts 2 and 9. Section numbers and a few details shift between editions, so always confirm the edition your jurisdiction has adopted with your local authority having jurisdiction.
Emergency lighting and exit signs do two different jobs
Emergency lighting illuminates the walking surface along the route out of the building so people can move safely during a power loss. Exit signs mark the direction of travel and the exit doors themselves. A building generally needs both, and the codes treat them as separate requirements with their own rules.
The 90-minute rule
On a loss of normal power, emergency illumination has to come on automatically and stay lit for at least 90 minutes. The transfer to backup power has to happen fast, within about 10 seconds, so the space is never left dark. That 90-minute window is why battery backup units, emergency drivers, and inverter systems are sized the way they are, and it is the duration your annual test has to prove.
How much light the exit path needs
The codes set both a normal level and an emergency level for the means of egress, measured at the floor along the path of travel.
| Condition | Average | Minimum at any point |
|---|---|---|
| Normal power, space occupied | At least 1 foot-candle at the walking surface | Set by the path; stairways are held to a higher level in California |
| Emergency power, initial | At least 1 foot-candle | At least 0.1 foot-candle |
| Emergency power, end of 90 minutes | Not less than 0.6 foot-candle | Not less than 0.06 foot-candle |
There is also a uniformity limit: the ratio of the brightest point to the darkest point along the path cannot exceed 40 to 1. That rule stops a design from meeting the average with a few bright pools while leaving dark gaps in between. In practice it drives fixture spacing on long corridors and in large open areas.
Where emergency lighting is required
Emergency illumination applies to the full means of egress: the exit access (the aisles, corridors, and ramps leading toward an exit), the exits themselves, and the exit discharge (the path from the exit to a public way outside). Which occupancies trigger the requirement is set by the individual occupancy chapters of the code, so a small business tenant space and a large assembly hall can face different thresholds. Confirm the trigger for your specific occupancy and edition rather than assuming.
Exit sign rules
Exit signs have their own set of requirements that inspectors check closely:
- Letter size. Lettering is at least 6 inches tall, with a principal stroke width of at least 3/4 inch, so the word reads from a distance.
- Illumination. Signs stay continuously illuminated whenever the building is occupied, and they remain lit on emergency power for the same 90 minutes. Externally illuminated signs are lit to at least 5 foot-candles at the sign face.
- Placement and viewing distance. No point along an exit-access corridor can be farther from the nearest visible sign than the sign's rated viewing distance, or 100 feet, whichever is less. Additional directional signs fill any gap where the path or the exit is not obvious.
- The "no exit" rule. A door or passage that could be mistaken for a way out, but is not, has to be marked so no one heads the wrong way in a hurry.
Testing and records
Emergency and exit lighting has to be tested on a schedule, and the records matter as much as the test:
- A functional test of at least 30 seconds every month, to confirm the units switch over and light up.
- A full 90-minute test once a year, to confirm the batteries actually carry the load for the required duration.
- Written records kept by the building owner for the inspector to review.
Self-testing and self-diagnostic fixtures can automate these checks and flag a failure on the unit itself, which cuts down the manual labor of walking a large building every month.
Buy equipment that carries the right listing
Emergency lighting hardware is listed to UL 924, the safety standard for emergency lighting and power equipment. That listing covers battery backup units, emergency drivers and ballasts, exit signs, transfer devices, and inverters, and it verifies the 90-minute duration, fast transfer, and illumination performance the codes rely on. When you order, look for the UL 924 listing on battery backups, emergency drivers such as Bodine and other emergency-ballast lines, replacement backup batteries, and exit signs. Rock also stocks the broader safety and security category for related life-safety gear.
A note on California and Title 24
It is a common mix-up, so it is worth being precise: the light levels and the 90-minute duration are building and fire code requirements (the California Building Code and Fire Code, and NFPA 101), not energy code requirements. Title 24, Part 6, the energy code, governs lighting controls. It lets you reduce egress lighting with occupancy sensors and daylighting, but the building code still requires the path of egress to stay at least 1 foot-candle whenever the space is occupied, and it cannot be fully switched off while people are present. If you are designing controls, the two codes work together: save energy where you can, but never below the life-safety floor. Our guides to Title 24 daylighting and Title 24 outdoor controls cover the controls side in more depth.
Frequently asked questions
How long must emergency lighting stay on during a power outage?
At least 90 minutes. When normal power fails, emergency illumination has to switch on automatically within about 10 seconds and keep the exit path lit for a minimum of 90 minutes.
How much light does the exit path need?
Under emergency power the path starts at an average of 1 foot-candle with at least 0.1 foot-candle at any single point, and it may decline to an average of 0.6 foot-candle and 0.06 foot-candle minimum by the end of 90 minutes. The ratio of brightest to darkest point cannot exceed 40 to 1.
Do exit signs have to stay lit all the time?
Yes. Exit signs are continuously illuminated whenever the building is occupied, and they have to stay lit on emergency power for the same 90 minutes as the rest of the egress lighting.
How big do exit sign letters have to be?
Lettering is at least 6 inches tall with a principal stroke width of at least 3/4 inch. Externally illuminated signs also have to be lit to at least 5 foot-candles at the sign face.
How often does emergency and exit lighting need testing?
A functional test of at least 30 seconds every month, plus a full 90-minute test once a year, with written records kept for the inspector. Self-testing units can automate these checks and report a failure on the fixture itself.
Does California Title 24 set the light levels for egress?
No. The light levels and the 90-minute duration come from the building and fire codes and NFPA 101. Title 24, Part 6, governs lighting controls and allows occupancy-based reduction, but the path of egress must stay at least 1 foot-candle while the space is occupied.
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This guide is general information, not a substitute for the adopted code. Emergency and exit lighting requirements vary by code edition and jurisdiction. Confirm the specific requirements for your project with your local authority having jurisdiction.