Audibility in a Nursing Home Corridor and Resident Rooms
A 60-bed nursing home has an 80-ft-long corridor with an 8-ft ceiling. Two horn/strobes are spaced 40 ft apart. With the corridor quiet at 55 dBA ambient, the measured sound pressure is 70 dBA at 10 ft from the nearest horn. Private resident rooms open directly off the corridor; each room is 20 ft deep with a solid door and a 1-in. undercut. The fire alarm is conventional, and the owner wants to add only a sounder base in the two rooms closest to the nurse station. The AHJ has cited the system for inadequate audibility in resident rooms. The corridor is public mode; resident rooms are sleeping areas.
1. Evaluate the corridor measurement against the audibility requirement for the resident sleeping rooms.
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The corridor measurement of 70 dBA at 10 ft does not demonstrate compliance in the sleeping rooms. For sleeping areas, NFPA 72 requires a sound level of at least 75 dBA at the pillow, or 15 dBA above the ambient sound level, whichever is greater. The corridor is already below 75 dBA. More importantly, the corridor level is not the pillow level. A solid door with only a 1-in. undercut will attenuate the signal substantially, commonly on the order of 15 to 20 dBA, so a room could receive roughly 50 to 55 dBA while the alarm is sounding. Even if the room ambient is only 35 to 40 dBA and 15 dBA above ambient would be 50 to 55 dBA, the 75 dBA sleeping-area criterion governs. The system is therefore not adequately audible in the resident rooms, and the AHJ's citation is supportable.
2. Is adding sounder bases in the two rooms nearest the nurse station sufficient?
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No. The two rooms nearest the nurse station are not representative of the other 58 beds, and the correction must provide adequate audibility in each resident sleeping room. Sounder bases can be an acceptable method only if they are listed as compatible with the panel, are synchronized with the corridor horns, produce at least 75 dBA at the pillow, and are powered within the NAC capacity. The contractor must calculate the added current and voltage drop; a conventional panel with an existing 2.0 A or similar NAC may not support sounder bases in every room. If sounder bases cannot meet the pillow level, in-room speakers or other listed appliances are needed. The design should be room-by-room, not limited to the rooms closest to staff.
3. What should be checked for visible notification and synchronization?
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The corridor is a public-mode area and must have visible notification coverage for hearing-impaired occupants in accordance with the accessibility requirements and the AHJ's interpretation. Resident sleeping rooms may require private-mode visible alarms where accessibility requirements apply; the design professional should confirm the required rooms with the AHJ rather than assume that only corridors need strobes. All newly installed visible appliances must be synchronized if they are in the same field of view, and the synchronization must be compatible with the existing panel. The contractor should verify strobe intensity and spacing using the manufacturer's coverage tables for the 8-ft ceiling and 80-ft corridor, not simply match the horn spacing. After installation, test audibility at the pillow in each room, verify visible coverage, and document the results.