You have three choices. (A)expend the effort to locate the source of this noise-i.e. rethink "risking falling thru the ceiling and disturbing...insulation" and find the #$%^ thing. (B) hire a (presumably insured)professional to do option (A). (C) "continue to let them chirp several times a day"...(and if you are lucky the source of the noise isn't some hardwired device). I would find the source one way or the other, it wouldn't be the first drywall repair for me.

Thank you for the responses. I bought all new units just alike. Didn't get the CO combo, with no natural gas in home don't think they are necessary....may be wrong on that. At any rate, I called our local fire department to ask about the best units to get and if they could recommend anyone to install for me. To my surprise they said they would come and install and they did yesterday afternoon! Two guys, one a volunteer and one on county payroll. Took them about 15 minutes. I paid close attention and bus driver, you are right, I could do it, and will in my house. Just to pass it along, check with your local fire department, they too may have a program to help you with these things. In fact he offered me three of the battery operated smoke detectors as part of their program. And again, tax dollars at work for ME. Thanks again for your responses. Murphy

lol. Interestingly enough if he were going to remove just one wire, I would have removed the black one... Either way, it's not a bomb. It is, however, a hazard to have ANY live wires "sticking out" or otherwise not properly "ended". If you choose to get rid of the hardwired smoke detector altogether, "cap" the wires with "wire nuts" and put a blank round plate over the hole (you can buy the plate at almost any hardware store. Don't try to make one yourself. Same with wirenuts.) Installing a new hardwired one is similarly simple. Match black to black, white to white, attach with wires, and secure it to the wall/ceiling per the instructions (usually two screws). I haven't seen a smoke detector with a ground wire since the early 80s, but if you somehow manage to find one, it'll have a green wire that needs to be connected to the bare copper wire in the wall/ceiling, also with a wirenut. No matter which option you choose, you'll want to turn off the power before mucking around with them wires. Since you probably have no reliable way to TEST them, I'd recommend turning off the power to the entire house.

Thanks for posting that section, Fred! I've been having trouble finding the right section in the codes, most of the things I've come across have been from secondary sources writing about the codes. Always loses some detail in the translation. I think exception 3 should apply to my situation, but with a twist (there's always a twist). I looked through the permit documents the city has available online, and it looks like there were two separate permits for downstairs work. The first permit related to the portion of the downstairs where the alarms are actually located, and was described as "Remodel existing space behind garage, no enlarge of existing habitable space." I'm assuming if walls had been removed, that would have been indicated in the description (no idea if that's a safe assumption or not). The second permit was a issued a year later, and relates to the other end of the downstairs area, i.e., away from the alarms. That permit was described as "Remove bearing wall next to stair on ground floor." So there was a wall taken out downstairs at some point. Did removing that wall negate the code exception for the entire downstairs, such that removal triggered the need to install wired alarms throughout the downstairs area? Such an outcome would seem pretty draconian, since it would require a significant tear down of areas that are nowhere near the permitted work area. I'm really impressed by the responses on here as a whole. My wife and I had used Houzz in the past primarily to get ideas for decorating/remodeling, had no idea there was such a great user community.