Q: If a smoke detecting device is disabled for a breathing treatment (often for several days), what sort of fire watch, notification or signage is necessary?
A: None. Fire watches are not for a single device taken out of service, or for a single device found to be impaired. According to section A.188.8.131.52 of the 2012 LSC, it is not the intent of the Life Safety Code to require notification of the AHJ or evacuation (or fire watch) for the portion of the building affected for a single nonoperative device or appliance.
Also, section 184.108.40.206 of the 2012 LSC says where a required fire alarm system (not a single device) is out of service for 4 or more hours in a 24-hour period then an approved fire watch should be conducted. If this smoke detector is located in a healthcare occupancy, there may be a good chance that it is not a required device. Many designers add smoke detectors throughout hospitals where the LSC does not actually require them. In my opinion, you would need to have a branch or circuit disabled on a fire alarm system before a fire watch is required.