Smoke Detector play a vital role in providing your family and home with the protection needed to avert a disaster in case of fire. NOTOFIRE NF111 Photoelectric Smoke Alarm is a completely wireless and standalone smoke detector. Since it is an independent - battery-operated - fire detector, it can be installed easily by yourself with some screws in the ceiling or roof. We recommend installing at least one smoke detector or fire alarm in every room. NF111 Photoelectric Smoke Alarm comes with a replaceable 9V lithium battery and a powerful sensor with a service life of 10 Years. This smoke alarm also comes with a safety test button to test the smoke alarm periodically. It also rings a warning alarm for low battery. NOTOFIRE NF111 Photoelectric Smoke Alarm sounds the alarm at 85 dB as per the recommendation of NFPA. NOTOFIRE NF111 Photoelectric Smoke Alarm has a highly sensitive omnidirectional optical chamber and it works on photoelectric principles. This means it is highly responsive, especially in the case of smoldering fires, and does not contain any radioactive substance. So it is an environment-friendly smoke sensor.