Types of detectors used in fire alarm

These types of detectors used in fire alarm system
1. Smoke detector
2. Heat detector
3. Flame detector

Placement of fire detectors

1. In general fire detector are normally placed on the ceiling or within 12″ of ceiling.
2. Where possible the detectors should be located throughout entire building.

Smoke detector
1. A smoke detector is a device that senses smoke, typically as an indicator of fire
2. The smoke detector detect the presence of the smoke

Types of smoke detectors
1. Photo electric smoke detector
2. Ionization smoke detector

A. Photo electric smoke detector
The photo electric smoke detector is work on the light sensitive sensor this sensor the sense a smoke and other combustible material .

B .Ionization smoke detectors
Ionization smoke detector is work on the radioactive material between two electrically charged plate and this electrical plates middle distance is detect the air and smoke.

Heat detector

1. The heat detector respond to the excess that generate in the fire
2. The heat detector detect the presence of a heat

Types of heat detector

A. Fixed temperature heat detectors
B. Rate of rise heat detectors

A. Fixed temperature heat detectors
This is the most common type of heat detector. Fixed temperature detectors operate when the heat sensitive eutectic alloy reaches the eutectic point changing state from a solid to a liquid

B. Rate of rise heat detector
This type of heat detector can operate at a lower temperature fire condition than would be possible if the threshold were fixed. It has two heat-sensitive thermocouples.

Flame detector :
1.  A flame detector is a sensor designed to detect and respond to the presence of a flame or fire

2. A flame detector can often respond faster and more accurately than a smoke or heat detector due to the mechanisms it uses to detect the flame

Types of flame detector

1. Ionization current flame detector
2. Thermocouple flame detection

1.Ionization current flame detector
The intense ionization within the body of a flame can be measured by means by the phenomena of Flame Rectification whereby an AC current flows more easily in one direction when a voltage is applied. This current can be used to verify flame presence and quality.

Such detectors can be used in large industrial process gas heaters and are connected to the flame control system

2. Thermocouple flame detection

Components of fire alarm system

1. Power supply
2. Detectors & manually pull boxes
3. Signal supervisors

Components to a fire alarm system
1. Local alarm
2. Indicator boards
3. Reference for alarm system.