Detectors are devices that detect fire. Fire alarm sensors (depending on which fire attributes are sensitive) are located in smoke
sensor groups, heat sensors, carbon monoxide sensors, flame sensors and combined sensors. Types of fire detectors are:
This category of detectors includes an optical cell (cell) and a light source, a lens to regulate the illumination of the inside of the enclosure
and a photodiode (or other sensors) Photoelectric (electric photo). The detector is constructed in such a way that, under normal conditions
of operation, light beams pass through the detector and stuck in the inserted cells. When smoke particles appear, a number of light scattered
by smoke particles are then received by the sensor diode, and then triggered by the detector and signaling the occurrence of fire by sending
signals to the control center or central unit.
Situations in which spot smoke explorers should not be installed:
- In places where the height is more than 5/10 meters.
- In the place where the cooking takes place, such as the kitchen (only a fixed thermal detector should be used).
- In places where the fire does not produce smoke particles.
- Room boilers and generators (it is better to use a constant radiation detector and combined detectors).
Ionizing Smoke Detector:
The ionization smoke detector has a chamber that is in contact with the outside air. The interior of the chamber is ionized by a radioactive
source (ionization is the stage in which air molecules become positive ions and negative electrons). Now, if a voltage is established between this
compartment, the ions move toward the opposite pole. Positive ions move toward the negative electrode and electrons move toward the positive
electrode. The motion of these electrons and ions creates an electric current. The amount of electricity flow depends on the shape of the chamber,
the radioactive source, the supply voltage, temperature and humidity. As the air enters the chamber, the flow of electricity decreases
(the presence of smoke particles reduces the amount of electricity flow). And triggers detector and detector activation.
Linear transmitter and receptor explorers - Thermal turbulence:
Of course, some optical detectors do not need to be closed. In this way, a wide area (such as a sports hall, conference hall, etc.) is composed of
a receiver in one direction and a transmitter of light from the other side. The way of operation, the permanent radiation from the infrared rays
is sent from the sender to the receiver. As soon as the beam is interrupted or weakened by the smoke or any other object, the fire alarm system
will be sent to the control center and the fire alarm system will be activated. Because this device uses detectors with a warm airflow of smoke
through an optical radiation, they are considered to be thermal turbulence.
A. Fixed heat dissipation
B- Incremental thermal explorers
This detector is sensitive to temperature rise. When the ambient temperature changes due to the fire, this detector is activated.
The thermal detector has a chamber. There is a metal bar inside. Hot air affects the biometal and the heat closes its contacts and
the detector operates. This detector is suitable for places like kitchens, engine rooms, etc.
These detectors detect and activate the invisible optical wave emitted by the flame. These detectors have a clear viewing angle that should
be considered when designing and operating.
These detectors are of respiratory and smoke detectors and are sucked through the tubes around the surrounding environment and
sucked into the laser beam by a strong ventilator into the detector chamber. There are also differences between laser explorers, and in
some of them, they focus laser radiation at a central point in the middle of the compartment, and the air sucked into the explorer will be passed
directly from that point.
Also, in terms of the particle size and number of particles, they are also examined and then with the recorded data from the explorer's
memory, if the particle concentration is exceeded, the detector is activated and the fire is triggered.
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