I had that with a couple of clients, I always bung in a couple of free smoke detectors on a repaint or small worksIs that a dentist thing? Our dentist had a smoke alarm that went beep every few minutes. It remained the same, (or happened again 'cos they buy crap batteries) for a couple of years until they redecorated.
good ones from the suppliers
but they had taken the batterie sout as they kept beeping, found out they had both purchased KODAK batteries
made in China in batches, probably sitting around for years, reading 7.8 volts new out of the pack
I bought a box of new ones from the wholesaler and changed them free