The Kidde 29HD Optical Smoke Alarm is battery operated and has a loud 85 dB alarm that will sound when smoke is detected. It also features a test button to allow for regular testing of the alarm function and a Hush button for temporarily silencing nuisance alarms. The alarm can be easily installed in most locations within your home, particularly in bedrooms and living areas. The optical smoke sensing technology means that this alarm is highly effective at detecting slow-burning fires, and less susceptible to false activations caused by cooking fumes. Approved to EN 14604 and CE marked. It comes with a 5 year manufacturers warranty. Supplied with a 9V Battery.