Today, there are a lot of cases of fire in the premises. Due to the fact that modern technology does not stand still, there are currently various ways to protect against sudden fire. Few people pay attention to such a small hidden device as a fire detector. Usually they are installed on the ceilings of offices and apartments. These products are even specially designed in such a way as to merge with the situation and fit well into any interior. But the lives of people and the safety of property depend on these simple and inconspicuous devices.
Device Description
What is a fire alarm sensor? Let's dwell on this in more detail. In fact, calling it a sensor is not entirely correct, since only an element that reacts to thermal, light, chemical or other influences is considered to be a sensor. In addition to the sensor itself, the fire detectorincludes other elements. The device depends on the specific model. It may include signal recognition elements, communication system, reclosing structure and other components.
Classification
There are a huge variety of fire detectors of various types and types. You can classify them according to various criteria:
1. According to the principle of the emitted signal: the transmission system is a mandatory design element present in absolutely all fire detectors. The existence of the device itself without such a system would be meaningless.
The following devices stand out:
- Single-mode detectors: generate and transmit a fire signal with a sufficiently long exposure to an external factor, which is designed to track the fire sensor. Typically, such devices operate under the influence of high temperatures. Single-mode devices are hardly ever used at present.
- Dual-mode detectors: generate and transmit two signals at once - "Fire" and "No fire". It may seem to some that the signal that there is no fire is redundant, since the "Fire" signal indicates the presence of a dangerous situation in the room. However, everything is not so simple. The signal "No fire" notifies that the detector is in good condition and monitors the situation in real time. A malfunction of a single-mode detector about the absence of a fire can be found out only during the test. Every day no one arranges such checks.will. It is for this reason that dual-mode devices are more popular than single-mode devices.
- Multi-mode devices: a feature of this type of sensors is that they report a problem with a special type of signal. However, this does not mean that the detector is completely out of order. This quality is especially useful, even indispensable, at large facilities, where it will take time to find a faulty detector. Having determined the nature of the malfunction, the master will be able to eliminate it. The multi-mode device is also capable of generating other signals, such as "sensor dirty".
2. By type of signal transmission:
- Wired: the signal in such detectors is transmitted via cable.
- Wireless: Uses a radio signal or a mobile phone channel to transmit the signal.
3. By parameter change type:
- Differential: they give a reaction not to the absolute value of the checked parameter, but to its dynamics.
- Threshold devices: detect when a parameter monitored by a sensor reaches a critical value, after which an alarm is triggered.
- Combined units respond to both types of parameter changes.
4. By localization:
- Point: have one sensor assembled with the detector. Such devices are most often used in everyday life.
- Multi-point detectors: have several sensors at once.
- Linear: controls space along an arbitrary line. There are pairs and singles.
Also fire detectorsvary by sensor type. This type of classification should be considered in more detail.
Thermal type sensors
What makes them special? These heat detectors appeared a long time ago and for a long time remained the most common. The first fire safety devices, which appeared back in the 19th century, were a pair of spring-loaded wires separated by a wax insert. As the temperature rose, the wax melted, the wires connected and completed the circuit, thus triggering the alarm.
Modern fire safety sensors usually contain fusible elements. Other triggering principles can also be used, such as the thermoelectric effect. It occurs at a certain temperature at the junction of two different conductors (thermocouple). The most common sensors that were installed in Soviet high-rise buildings are based on this principle.
With all the advantages of thermal sensors, they have one significant disadvantage: the air temperature increases significantly only when the flame has already flared up. Therefore, such devices are gradually losing ground.
Smoke detectors for fire alarms
What are they and what is their speci alty? Fire smoke sensors today are confidently leading in alarm systems installed in administrative and residential buildings. After all, the first sign of a starting fire is smoke. It may even appear beforethe occurrence of a fire. For example, electrical wiring under conditions of low oxygen levels for a long time may be in the smoldering stage.
How do fire detectors (fire smoke) work? The principle of operation is based on changing the transparency of smoky air. Linear detectors emit a directed beam of light in the optical or ultraviolet range. A beam of light in conditions of normal transparency freely passes the segment of the tracked space intended for it and hits the reflector. If the smoke blocks the path of the beam, then the photocell will fix this and the detector will emit a signal.
A point emitter emits beams of infrared radiation into space, scattered by air, which is completely transparent in the optical spectrum. However, for a range, it is not. An infrared beam with low intensity simply will not be able to reach the nearest obstacle and be reflected to the detector. When connecting detectors, it is important to observe the minimum distances from the sensor to an obstacle. The smoke emitted during smoldering reflects infrared rays well. The beam reflects off the smoke-filled area, triggering the fire protection.
The fire alarm point sensor has a simple device and is relatively inexpensive. However, they also have their drawbacks. Such sensors are not very reliable. For example, thick black smoke does not reflect, but absorbs infrared rays. Therefore, when burning rubber and diesel fuel, suchdetectors may be ineffective.
Flame detectors
What are they? A fire detector that reacts to a flame is usually installed in industries where heat and smoke emitters cannot be used due to certain specifics: high air temperature, smoke or dust in the air.
According to the principle of operation, flame sensors can be infrared. Such devices capture the radiant heat emanating from the flame. In a room where sources of infrared radiation, such as heaters, are constantly working, it is better to use ultraviolet flame sensors. There are also devices that respond to the electromagnetic component of the radiation of an open flame. Such a sensor is able to recognize fire even at a great distance.
Security ultrasonic motion sensors may well be used as fire detectors. The principle of their operation is based on the recognition of the nature of the propagation of ultrasound in stationary and moving air. The flow of air masses can be caused not only by the actions of the intruder, but also by fire. For this reason, ultrasonic sensors may well indicate the start of a fire.
Now that you know about the main types of fire detectors and how they work, you can begin to consider the rules for their installation.
Fire alarm installation
Let's take a closer look at this aspect. How to install fire detectors in an apartment? To devicereacted to the fire as it should, it is necessary to take into account a lot of features. The main ones are listed below:
- It is best to mount the fire detector on the ceiling. If the design makes installation difficult, then you can fix them on tension cables or columns, at a distance of no more than 30 cm from the ceiling.
- One electrical circuit can combine no more than 10 devices for administrative premises and residential apartments and no more than 5 devices for production. When using the addressable connection scheme, the number of devices in one loop can reach 20.
- If there are objects in the room, the upper edge of which is at a distance of less than 60 cm from the ceiling, be sure to place the detector in each of the zones formed by such objects.
- The area controlled by the device must correspond to the values given in the data sheet of the specific model.
How to choose a fire alarm?
This aspect should be given special attention. Today, many people want to have fire detectors in their homes. Systems of this kind can differ in many ways. The cost of the detector should not be a decisive criterion for selection. For installation in city apartments, it is better to use addressable devices. The complex architecture of the room makes it difficult to use stand-alone systems. When using addressable detectors, it is better to connect to the control device in a radial pattern. If the loop wires are hidden behind false walls or suspendedceiling, then the space between the ceiling and the cladding must be in the control zone of the detectors connected to a separate loop.
Fire detectors should be installed in such a way that, in the event of a malfunction, they can be easily removed from the wall and replaced.
Installation
So what's special about him? Fire smoke sensors are installed in accordance with the plan and wiring diagram. Installation of such systems is best left to specialists. Sensors can be connected in a triangular or square pattern. When installing, it is important to take into account the distance between opposite walls, as well as between sensors. For example, if the height of the room is less than 8 meters, the distance between the thermal sensors should be 7 meters when using a square arrangement and 8.6 meters when using a triangular arrangement. The distance between the sensor and the wall should be 3.5 and 2.5 meters, respectively. If the height of the room is between 8 and 11 meters, these schemes can only be used in special cases.
Fire smoke detectors can be installed in a square or triangular arrangement only in case of high room height. If it reaches 11 meters, the distance between the sensors should be 10.5 meters when using a square circuit, and 13 meters when using a triangular circuit. The distance between the wall and the sensor is 5.3 and 3.75 m respectively.
How should the sensors be installed? The fire protection system can beorganized in three patterns:
- Targeted: allows you to accurately identify the place of fire.
- Analog Addressable: Allows for better response speed in the event of a fire.
- Threshold: Only used in small spaces.
Connection
Let's take a closer look at this. What do you need to connect a fire alarm sensor? The main elements of such systems are a power supply, a control device, an indication unit, control equipment and the sensors themselves. Nevertheless, it is not always possible to install such classical systems. There are many objects on which it is impossible to install complex alarms. However, fire detection systems on them are still necessary for fire safety. To solve this problem, autonomous fire detectors can be used. Such systems are connected to self-contained power devices and can be removed from fixed loops of warning systems.
The simplest example of this design is a battery fire detector. It can be installed both alone and as part of a single system. One device allows you to organize a fire protection system in a room up to 50 square meters. The alarm is activated as soon as the smoke enters the air chamber. At the same time, a sound and light signal appears. The system is powered by batteries with voltage up to 9 V.
Basic parametersdevices
Let's take a closer look at them. If you want to install fire detectors in an apartment, you need to pay attention to the following device parameters:
- speed of reaction to ignition;
- energy costs required to operate the system;
- element sensitivity;
- Catcher customization;
- sensor mounting method;
- operational safety;
- system maintenance method;
- corresponding to the height and area of the room;
- possibility of using autonomous power sources.
Conclusion
Today, a fire detector must be installed in residential and administrative buildings. This simple security measure could one day save your life. In new houses and apartments, such systems are usually planned at the design stage. If your home does not have fire detectors, you can install them yourself.
