Smoke detector, gas detector, heat detector, CO detector and compound detectors are used in fire alarm system. But false alarm caused by these detectors also led to serious loss. The worst is, false alarm in return caused misunderstanding of fire alarm system and people stop using it. People will remove the battery and not install it again if false alarm occurs. People may ignore real fire alarm if false alarm ever occurred.
It is impossible to completely eliminate false alarm. But we need to know the causes of false alarm and reduce the rate. The compulsory certification, ISO9001, ISO9002 standard implemented for products manufacture largely reduced false alarm rate. New technology analog fire alarm system, MCU processing detectors also reduced false alarm rate. But another main factor for false alarm of fire system is environment interference and misusing of the detectors. 7 causes for false alarm of fire alarm system are summarized as blow.
1.Non fire smoke but dust factors
A.Cooking oil fume. If the smoke detector is installed in kitchen and near the oven, the smoke detector especially the ionization detectors will make false alarm. So, smoke detector can not be installed in kitchen. Heat detector and gas sensor should be installed in kitchen.
B.Smoking. For high sensitivity smoke detector, smoking may cause false alarm. So, the sensitivity should be adjusted according to environment or people should be noted without smoking at the place.
C.Steam. Smoke detector installed in bathroom may cause false alarm by steam. So, install heat detector instead of smoke detector in bathroom.
D.Dust. Smoke detector can not be installed at heavy dust circumstance.
Insecticide. Aerosol insecticide and air freshener may cause false alarm.
B.Airflow. Airflow may interferes ionization detectors more than photoelectric detectors.
C.Rapid temperature changes. The heat detector and compound detector can not be installed near the air conditioner or heater device outlet.
3.Quality of detectors
A.Design quality of the detectors.
Fault tolerance: the ability of system software to maintain normal operation under the action of known and unpredictable accidents.
Tolerance: the ability to maintain the system performance unchanged when the parameters of the system hardware components are discrete.
Environmental sensitivity: the ability of the system to maintain stable operation in the mechanical, climatic and electromagnetic environment which is stipulated in the national standards and is potentially used in practice.
B. Manufacture quality of the detectors.
Automatic manufacturing process, ISO processing standard implement and certification test largely increased detector quality and reduces interference and false alarm.
Someone smoking face to the smoke detector or push down the manual call point on purpose.
Not obey the detector using rules.
5.Engineering project design fault.
Project design engineers are not technology certificated and made improper or wrong configure of the fire security project.
A.Installation location is wrong or not suitable.
B.Improper type detectors installation. For example, smoke detector is not suitable for garage and smoking room installation.
6.Poor installation of the fire alarm system
NFPA72 National Fire Alarm Code Chairman of the technical committee Wayne.D.Moore said that the main cause of false alarm is poor installation quality and pollution during construction. The fire alarm system should be installed after interior decoration of buildings to avoid pollution. The detector cover can prevent accidental mechanical damage and surface contamination only.
A.The fire alarm system is not earthed or well earthed. It makes the system vulnerable to electromagnetic interference and cause false alarm.
B.The construction quality is poor, the line insulation can not meet the requirements, the contact pressure of the connection is not good or the wiring is improper.
7. Component aging, dust accumulation and insect invasion.
Component aging will reduce system reliability and make false alarm. Detectors with more than 10 years using time should be replaced or rechecked before use again. Detectors should be cleaned every one year. Dust proof, moth proof design for the sensing cavity.