A smoke detector is a portable device that senses smoke, usually as an indicator of smoke. Smoke alarms are usually smaller than smoke detectors, usually just shaped like a hard disk about 150mm (6in) in diameter and not more than 25mm (1in) thick, although shape and size also vary. Most smoke detectors can be activated either manually or automatically. Manual activation is normally done by pressing a button on the side, while automatic smoke detector activation can be done by hitting a switch, dial or push a button.

Smoke alarms that work with addressable systems are far more advanced than those that use opt-in combinations. While both addressable and opt-in combinations allow a person to program the detector to respond to certain triggers, an addressable system has an integrated alarm system that can be programmed to react only to specific people, rooms or certain types of situations. For example, a smoke detector can be programmed to detect smoke coming from the house over a door leading out into the backyard, or to be sensitive enough to activate only when children are in the area or when an unattended pet enters the house. Most smoke alarms can also have other special functions, such as flashing lights if there is fire in the kitchen, or having the siren ring at the exact time the fire alarms sound in an occupied building.

Common Types

The most common type of smoke detector is the battery-operated ionization detector. These detectors have been on the market for many years, and are relatively inexpensive. They consist of two parts: a power source and a pair of conductors that have positively charged contacts on their outer edges. When a current is applied to these contacts, the electrons travel from the negative to the positive sides of the contacts, emitting a radio signal whenever a molecule of their electrified opposites (an element with a positive electrical charge) comes in contact with them.

Ionization sensors have many advantages. Since they do not require batteries to function, they are incredibly reliable and will function for years without ever needing to be replaced. Also, because they use only one type of internal radio transmitter, it is extremely easy to install a smoke detector sensor and have an alarm going when a fire alarm in another part of the building goes off. Some fire alarm systems may require multiple batteries to operate, so an ionization detector can be used as a backup to a fire alarm in case a battery backup is not available.


A more recent technology that is very popular is the fire detection and notification system based on piezoelectric frequencies. The main benefit of this type of smoke detector is that it does not require an external battery. Instead, it works by detecting changes in pressure when a substance such as fuel drops into a container. Like ionization sensors, the emitted radio frequency waves come from only one source, so they are more reliable. These types of devices usually measure the inside of objects and are good for interior rooms where an alarm would be ineffective since they are able to detect the faintest amount of smoke.

There are several different models of Homekit smoke detectors in Canada that all utilize different technologies, which makes choosing the right one somewhat difficult. Before purchasing a smoke detector, you should first determine how sensitive your device needs to be and how many particles per square meter of area it can detect. In general, you should get a detector that can detect smoke particles up to two micrometers in size. The number of decibels is measured in decibels and this number indicates the potential energy of the molecules of smoke. The higher the decibel level, the greater the potential energy.