Smoke detector types and their working principle

A device that detects smoke and generates a signal to create an alarm and alert people in the vicinity or alert the fire safety panel (from where fire safety department response starts). The signal can be a local alarm or intimate fire safety Panel. Smoke detectors are considered to be the first choice when we talk about fire safety because detection and warning are the two main and strategies of fire safety through which we can save lives and property within a safe period of time when there is a real fire incident.

There are two types of smoke detectors classified them on the basis of their working principle as under;

1. Ionization Smoke Detector 
2. Optical Smoke Detector

Let, proceed to discussed the purpose, working principle, and other important details of smoke detectors in detail.

What is the purpose of a Smoke Detector?

The main purpose of a smoke detector is to detect smoke and intimate people in the vicinity ad send a signal to the control panel for further action (the second feature is only for the detector which is connected with fire safety panel).

It always recommended that the detector without fire safety panel must be only used in simple and residential facilities where the risk of fire is moderate to low range. While for commercial and complex facilities the detector must be accompanied by fire safety panel so that if the fire ignites it can detect and extinguish before it grew uncontrolled and cause losses.

TYPES (Operating System)

The shape and size of the different smoke detectors are almost similar and we can not distinguish them easily but there are mainly two types of the operating system on the basis of which we can differentiate.

Ionization Type Smoke Detector - Working Principle

The ionization smoke detector contains a small amount of radioactive element between two electrodes plates.

The amount of radioactive element in ionization type smoke detectors is kept very small (approximately 1/5000th of a gram or 1 Curi ) of americium - 241. The element has a half-life of 432 years and it emits alpha particles in good numbers.

The radioactive element ionized air molecules between them which results in an uninterrupted flow current between electrodes. When a fire ignites in the detector vicinity and smoke reaches the chamber the flow of ions between electrodes is disturbed and blocked by an increasing amount of smoke in the chamber. Hence, the reverse circuit activates and generates an alarm locally or sends a signal to the mother panel.

Optical Type Smoke Detector - Working Principle

The optical Type smoke detector works on the light-sensing and scatters principle as the detector camber contains two important elements 1) a light-emitting diode (LED) powered by a battery and 2) a photodetector diode. In the normal condition, the photodetector detects the uninterrupted light coming from the light-emitting diode. When fire ignite and smoke reached chamber it interrupted the light between LED and photo-detecting diode, this alert the circuit to generate an alarm. In some smoke detectors, this feature is further advanced by adding smoke density measuring devices to avoid false alarm

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Where should Place Smoke Detector?

The smoke detector must be placed after performing a fire risk assessment of the facility where smoke detector installation is intended. Because, the wrong positioning of the smoke detector is can harm in two ways, firstly the cost of smoke detectors if it is position is not recommendable and secondly the risk of fire which can not be detected. The doctor should avoid placing onto the below locations;

1. In corners of any room or hall
2. Above kitchen oven or stow because there is always a chance of false alarm
3. A smoke detector should avoid in washrooms because the water vapors can cause a false alarm
4. Smoke placement near exhaust fan is not recommended because the fan can easily keep the smoke away from detector and hence no detection will be there in real fire incident
5. Installation of the smoke detector near heating equipment e.g heater can trigger a false alarm, therefore, kept them on a recommended distance 

What are the standards?

An important guideline on the planning and installation of smoke detectors is available on NFPA which will help the reader further to install and make your family and community safe from fire hazards.

Use of Smoke Detector

Smoke detectors are used in a wide range of places after doing fire safety risk assessment. A few of these places can be list as under;

• Home
• Offices
• Shops
• Hotel
• Motels
• Restaurants
• Cinemas
• Clubs
• Classrooms
• Labs
• Hospitals
• Ships
• Airplanes
• Airports