False alarms and missed reports due to fire alarm system integration

According to China's national standards, the definition of false alarms is: No fire actually occurred, and the fire alarm device issued a fire alarm signal. According to international standards, the definition of false alarm is that the reported fire does not exist and does not exist. The cause of false alarms can be intentional, misoperation or accidental. Combine it to understand that whether it is the cause of the detector, or the environment, human factors, or other reasons, as long as there is no fire but reported a fire signal, are called false alarm.

The false alarm rate is the number of false alarms in the fire alarm system during the specified use conditions and deadlines. Usually expressed as the number of false alarms per million hours : false alarm rate = false alarm frequency / million hours (106 hours )

People are very concerned about the significant losses caused by false alarms to important public resources. Therefore, it has been suggested that the importance of false alarms cannot be overstated.

Since the advent of fire detectors, the industry has been focusing on false alarms as the focus of attention. Each detector manufacturer faces two requirements. First, the products they produce can report actual fires in a timely manner or as quickly as possible. Second, they can never make false alarms. However, due to the fact that the cause of false alarms is very complex, there are internal, environmental, and usage reasons. It is often impossible to achieve these two requirements at the same time. Even considering only product-related reasons, it is also very difficult to completely eliminate false alarms due to limitations in the technical level and factors such as price.

Causes of false alarms in automatic fire alarm systems

Causes of false alarms are complex and can be roughly classified into the following categories:

1 , product quality problems

Manufacturers currently many automatic fire alarm, some product specifications mainly the sensitivity to the environment alarm products non-fire factors (temperature, humidity, dust) due to drift or lack of ability to compensate automatically compensate low; various The effects of interference and line distribution parameters cannot be automatically handled and lead to false alarms . Such false alarms are more prominent in traditional alarm products.

In the production of everything from welding to debugging to inspection of finished products, a large number of manual operations were used, and the number of errors and hidden dangers greatly exceeded that of automated production. In recent years, large-scale enterprises in the industry have been gradually eliminating manual operations and have played a significant role in ensuring the quality of manufacturing.

The "three defenses" treatment is a top priority in the use of the environment in South China. The products that pass the 92 % RH40 °C and 96- hour tests specified by the national standards do not mean that they can operate stably in the southern regions of China. This is mainly because some manufacturers have not made any efforts to handle the "three defenses". It should be pointed out that the above provisions of the national standards are for general conditions of use. If you want to operate normally in the high temperature and high humidity conditions in the southern rainy season, the product's “three defenses” capability must be higher than the above national standards.

There is a clear gap between the material control and the requirements of ISO9001 , which makes false alarms or other problems in the actual use of the manufactured products. In order to completely solve this phenomenon, a lot of practical and meticulous work must be done.

2 , improper equipment selection and layout

(1) The sensitivity of the detector is not reasonable. As we all know , high-sensitivity detectors can alarm at very low smoke concentrations . On the contrary, the lower the detector's sensitivity, the higher the smoke concentration. Such as meeting rooms and other places where smoke tends to accumulate , high-sensitivity smoke detectors have been selected . This makes non-fire smokes cause false alarms due to the unreasonable choice of the detectors. As place high ambient temperatures, the choice of the constant temperature high-sensitivity detectors, will result in a high temperature under the influence of false alarms occur.

(2) Changes in the nature of the use of the site did not take into account changes in the type of fire detectors. If it was originally used in offices, shopping malls and other places to change to kitchens and saunas , the original smoke detectors should have been changed to constant temperature detectors without change . Smoke, steam, and oil mist were detected as fires due to non-fire factors. Signal and alarm.

(3) Select the fire detector temperature calibration point is too low. If the ambient temperature is high , detectors with too low a constant temperature point will generate false alarms.

(4) The position of the temperature detector is too close to the high-temperature light source , which is misreported due to the influence of the heat emitted by the luminaire.

(5) Smoke detectors are installed at or near vapor-prone locations , and are misreported due to water vapor affecting the normal detection of the detector.

(6) The photoelectric smoke detector provided with a smoke may be generated, a large amount of dust and dirt accumulation places, and may produce a vapor mist, generated during the process places smoke, normal smoke, dust, steam, oil The influence of non-fire factors such as fog makes the detector misreport.

(7) The selected detector failed to correctly report the fire condition in the detector area and misreported.

Reasons for missed report of automatic fire alarm system

1. Although the installation of the equipment did not violate the regulations , due to the influence of environmental characteristics , the smoke could not be effectively collected and the report was missed. If the smoke detector installation angle is too large , the wind speed is too large and other factors , resulting in smoke detectors can not act in time and missed.

2. The smoke detector is too close to the air outlet , the open doors and windows are too close , the protection area is too large , the storage items are too close to the detector , the fan is too close, and so on . These factors can make the smoke generated during the fire not be able to Effectively entering the detection chamber or entering too little smoke causes the detector circuit to malfunction and the detector to fail to report.

3. When the selection of differential temperature detectors is inconsistent with the fire characteristics and environmental characteristics , if the fire temperature rises too slowly, the detector will not respond and missed.

4. The detector missed due to long-term moisture failure.

The information in this article comes from the Internet and was reorganized and edited by China Rescue Equipment Network.