Ceiling Strobe Candela Chart — by Room Size & Ceiling Height
Minimum candela for a ceiling-mounted fire alarm strobe, by room size and ceiling height, per NFPA 72 Table 18.5.5.5.1 (2022 edition). Unlike a wall strobe, a ceiling strobe's requirement climbs with ceiling height. Only cells confirmed by two or more independent sources are shown; the sources disagree on the larger cells, so verify those against the code. Wall-mounted strobes use a separate table.
Ceiling-mounted strobe candela
| Max room size | ≤ 10 ft ceiling | ≤ 20 ft ceiling | ≤ 30 ft ceiling |
|---|---|---|---|
| 20 × 20 ft | 15 cd | 30 cd | 55 cd |
| 30 × 30 ft | 30 cd | 45 cd | 75 cd |
| 50 × 50 ft | 95 cd | — | — |
Why ceiling height matters here but not for wall strobes
A ceiling strobe throws light down and outward, so the taller the ceiling, the farther that light spreads before it reaches a standing or seated occupant — and the more candela it takes to deliver the required intensity at eye level. That is why the same room needs progressively more candela as the ceiling rises from 10 to 20 to 30 ft. A wall-mounted strobe sits in the 80–96 in band regardless of ceiling height, so its table keys on room size alone.
Ceiling mounting is the natural choice for open areas where a wall strobe would be too far from the center of the space, and it is required where a low ceiling cannot fit a wall strobe's lens at 80 in. For narrow corridors, neither room table applies — use the corridor spacing chart.
Common questions
How is a ceiling-mounted strobe sized?
A ceiling strobe is sized by both room size and ceiling height (NFPA 72 Table 18.5.5.5.1, 2022 edition). For a 20×20 ft room the minimum rises from 15 cd at a 10 ft ceiling to 30 cd at 20 ft and 55 cd at 30 ft — the higher the strobe, the more candela it takes to reach the occupant's eye level. A 30×30 ft room runs 30 / 45 / 75 cd across the same three ceiling heights.
What if the ceiling is higher than 30 feet?
Where the ceiling exceeds 30 ft, you either suspend the appliance at or below 30 ft or switch to wall mounting — the ceiling table stops at 30 ft. Very high spaces are common candidates for wall-mounted strobes sized by the wall table instead.
Why are some cells blank on this chart?
The published sources for the ceiling table disagree on the larger-room and taller-ceiling cells (for example, a 50×50 ft room at a 20 ft ceiling appears as both 95 cd and 115 cd across editions). Rather than average conflicting life-safety values, this chart shows only the cells confirmed by two or more independent sources and points you to the full code table for the rest.
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