Smoke detectors are one of the most important devices in your home and are often overlooked. There are two types of smoke detector systems. The first has smoke detector wiring that issues a signal to an alarm system that monitored by a paid outside alarm company. The second is your basic smoke alarm that issues an audible and/or visual alarm from the device itself.
Smoke detector wiring can be powered by a central fire alarm system, which uses a battery backup, or as is the case in many single family detached and multi-family homes. A smoke alarm is powered only by a single disposable battery.
In the United States, most state and local laws for new construction or upgrades are based upon standards established in the National Fire Prevention Association (NFPA 72) fire code for placement of smoke detectors in homes and businesses. In the United States, smoke detectors are required on every habitable level and in attics that are accessible, and within the vicinity of all bedrooms. In Canada, it is required that a structure have a working smoke detector on every level.