24 CFR § 232.591
Smoke detectors
February 22, 2021
After October 30, 1992, each occupied room must include at least one battery-operated or hard-wired smoke detector in proper working condition. If the room is occupied by hearing-impaired persons, the smoke detector must have an alarm system designed for hearing-impaired persons, unless the smoke alarm is connected to a central alarm system that is monitored on a 24-hour basis, or otherwise meets industry standards.
[57 FR 33850, July 30, 1992]