Fire alarm system in the context of Manual fire alarm activation

A security alarm is a system designed to detect intrusions, such as unauthorized entry, into a building or other areas, such as a home or school. Security alarms protect against burglary (theft) or property damage, as well as against intruders. Examples include personal systems, neighborhood security alerts, car alarms, and prison alarms.

Some alarm systems serve a single purpose of burglary protection; combination systems provide fire and intrusion protection. Intrusion-alarm systems are combined with closed-circuit television surveillance (CCTV) systems to record intruders' activities and interface to access control systems for electrically locked doors. There are many types of security systems. Homeowners typically have small, self-contained noisemakers. These devices can also be complicated, multirole systems with computer monitoring and control. It may even include a two-way voice which allows communication between the panel and monitoring station.

A fire drill is a method of practicing how a building should evacuate in the event of a fire or other emergencies. In most cases, the building's existing fire alarm system is activated and the building is evacuated by means of the nearest available exits, as if an emergency had actually occurred. Fire drill procedures may vary depending on the building type, such as hospitals or high rise buildings, where occupants may be relocated within the building as opposed to evacuating the building. Generally, the evacuation interval is measured to ensure that it is fast enough, and problems with the emergency system or evacuation procedures are identified so that they may be remedied.

In addition to fire drills, most buildings have their fire alarm systems checked on a regular basis to ensure that the system is working. Fire alarm tests are often done outside normal business hours so as to minimize disruption of building functions; in schools, they are often done when students and staff are not around or during the holidays where specialist fire alarm engineers test alarms in the building for repair if needed.

A smoke detector is a device that senses smoke, typically as an indicator of fire. Smoke detectors/alarms are usually housed in plastic enclosures, typically shaped like a disk about 125 millimetres (5 in) in diameter and 25 millimetres (1 in) thick, but shape and size vary. Smoke can be detected either optically (photoelectric) or by physical process (ionization). Detectors may use one or both sensing methods. Sensitive detectors can be used to detect and deter smoking in banned areas. Smoke detectors in large commercial and industrial buildings are usually connected to a central fire alarm system.

Household smoke detectors, also known as smoke alarms, generally issue an audible or visual alarm from the detector itself or several detectors if there are multiple devices interconnected. Household smoke detectors range from individual battery-powered units to several interlinked units with battery backup. With interlinked units, if any unit detects smoke, alarms will trigger all of the units. This happens even if household power has gone out.