Smoke detector selection
一、 Select the detector according to the characteristics of the fire；
1. In the early stage of the fire, there is a smoldering stage, which generates a large amount of smoke and a small amount of heat, with little or no flame radiation. Smoke detectors should be used.
2. Fires develop rapidly, generating a large amount of heat, smoke and flame radiation. Smoke detectors, temperature detectors, flame detectors or combinations thereof can be used.
3. Fires develop rapidly, with strong flame radiation and a small amount of smoke and heat. Flame detectors should be used.
4. The characteristics of fire formation are unpredictable, and pattern recognition test can be performed, and the detector is selected according to the test result.
二、 Select the detector according to the environmental characteristics of the installation site；
1. Relative humidity is more than 95% for a long time, the airflow speed is more than 5m/s, a large amount of dust and water mist are retained, and corrosive gas may be generated. Under normal circumstances, there is smoke retention, and organic substances such as alcohols, ethers, ketones and the like are generated. Ion smoke detectors should not be used in places.
2. It is possible to use a temperature detector when there is a possibility of smoldering or a fire that does not cause early warning. It is not suitable to use a temperature detector. If the temperature is below 0 °C, it is not suitable to use a temperature detector. Use a differential temperature detector.
3. Flame detectors should not be used in places with the following conditions:
A. A flameless fire may occur;
B. There is smoke spread before the flame appears:
C. The lens of the detector is easily contaminated;
D. The “line of sight” of the detector is easily blocked;
E. The detector is easily or directly or indirectly illuminated by sunlight or other light sources:
F. Under normal circumstances, there are open fire operations and x-ray and arc lamps.
三、 Select the detector according to the height of the room；
The sensitivity of the detector should be selected according to the performance of the detector and the place of use. Under normal circumstances (no fire alarm), the system does not have a false alarm. At present, most of the domestic high-rise buildings use photo-inductor temperature detectors, and only in some places, kitchens, generator rooms, garages and places with gas fire-fighting devices use temperature detectors.
In short, the detector selection should be based on the actual environmental conditions to select the appropriate detector to achieve timely and accurate alarm purposes.
The difference between ionic and photoelectric
First, let’s first understand what is a photoelectric smoke detector and the working principle of a photoelectric smoke detector. The photoelectric smoke detector is also called a point detector. The photoelectric smoke detector uses the smoke generated during the fire. An alarm device developed to change the basic properties of light propagation characteristics. The photoelectric smoke detector has an optical labyrinth and is equipped with an infrared radiation tube. When the smoke is smokeless, the infrared receiving tube can not receive the infrared light emitted by the infrared emitting tube, but if there is smoke entering the optical labyrinth, the smoke passes through the refraction. The reflection tube receives the infrared light, and the intelligent alarm circuit determines whether the threshold value is exceeded. If the threshold value is exceeded, an alarm is issued.
The ionized smoke detector has an ionization chamber. The radioactive element used in the ionization chamber, Am241,has an intensity of about 0.8 microcurie. Under normal conditions, he is in equilibrium, but if smoke enters. The ionization chamber then destroys this equilibrium relationship and alerts when the smoke concentration reaches a certain threshold.
Ionized smoke detectors are sensitive to the induction of tiny smoke particles, while photoelectric smoke detectors are just the opposite. Photoelectric smoke detectors are sensitive to the detection of slightly larger smoke particles, if the smoke generated by the fire is For larger particles, it is better to use photoelectric smoke detectors. If the smoke generated by fire is relatively small particles, then the ion-type smoke detector is better, so whether it is ion-type smoke detector or photoelectric type. Smoke detectors are good, this needs to be determined according to your needs, and can not be generalized which is better or not, we have to analyze the specific issues, according to the actual situation.
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