Purchased 4 First Alert Model P1210 Smoke Alarms and installed them......of the 4 installed, 3 have malfunctioned numerous times and always at night.....it is 4:00 AM and one just went off and woke up the whole house.. The only one that has never gone off is the one I would have thought would be the first....in a basement stairwell near the hot water heater and the furnace but it has never chirped. Disgusted to say the least.....crappy parts from China and assembled in Mexico…….