Review on SITERWELL 10-Year Smoke Detector with Photoelectric Technology, Built-in 3V Battery, Low Battery Warning and Silence Function, UL217 and GS508 Certified – Pack of 4 by Giovanni Bedjohn

3 of 4 did not work. The first activated as instructed while the other 3 did not activate and "didn't work". Didn't beep or turn red when they were supposed to activate after holding the button for 5-10 seconds. Pretty disappointing. I bought them specifically for the magnet backing and free hard wire installation, but now I have to buy new ones elsewhere. money thrown away. I also tried googling how to fix or troubleshoot them to enable them and nothing showed up.