- EARLY WARNING SMOKE DETECTOR: The optical smoke alarm makes protecting your home simple. The optical smoke sensing chamber works by 'seeing' smoke as it enters the alarm, perfect for slow burning fires with thick white smoke. - TOAST PROOF: The high performance optical sensors ensure the FireAngel SB1-R is less prone to false alarms from cooking fumes, so you can enjoy your breakfast in peace. - TEST/HUSH BUTTON: Press the large test button to ensure your Fire Angel smoke alarm is working properly. A loud, high-pitched sound will verify it. To silence a false alarm, press and hold the button for 5 seconds. - 1 YEAR BATTERY: Each battery operated smoke alarm comes with a 1 year, replaceable 9V battery. When the smoke alarm battery is low, the device will 'chirp' and the red.