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.
2.Environmental factor
A.Electromagnetic radiation. 
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.
4.Man-made factors.
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.
Tag Archives: fire alarm
Automatic fire alarm system terms of manual and automatic control
On the fire regulation, there are some equipment should be automatically controlled by fire alarm control center. They are fire pump, smoke exhausting fan, fire proof door and fire curtain. The fire pump and smoke exhausting fan can not only be automatically controlled by fire alarm control center, but also be directly controlled manually at spot. Manual control buttons should be set on both sides of the fire rolling curtain on the evacuation channel.
Why do these devices so important for fire fighting? These devices can extinguish early fire and prevent fire spreading. So, these devices should be automatically turned on or shut off immediately when fire occurs.
On the fire regulation, other devices are not required to be set as automatically controlling. For example, fire bell horn and fire broadcasting etc. should be manually triggered or linkage output triggered after confirmation or other signal is found. If fire bell and fire broadcasting goes off without confirmation, it may cause unnecessary fear for people if false alarm occurred.
In the water extinguishing system, the fire hydrant system is controlled by the fire hydrant button, the start button on the control center linkage controller and the pump button on the pump control box of the pump room. Any button of these three ones is pressed, it will start the fire hydrant pump. It is manually controlled and not automatically controlled. There may have automatic and manual mark on the state switching switch of the control cabinet in the pump room. The automatic here means started by remote controlling and manual means started by local controlling. In an automatic sprinkler system, there are automatic and manual mark on the control cabinet of the sprinkler pump in the pump room. “Manual” means “on-site start” and “automatic” means manual start-up of the pump or pressure switch on the wet alarm valve of the control center. For the whole sprinkler system, “automatic” refers to the pressure switch start-up, and “manual” refers to the control center remote control start-up.
For pipe network gas fire extinguishing system, the release of fire extinguishing gas must be confirmed by people on the scene. Automatic state of fire identification is equipment confirmation. Its general practice is two sets of detectors at the same time issued alarms, can be considered as a fire start signal. When the first set of detectors alarm, the personnel on duty should immediately rush to the scene to make a manual confirmation on the spot to decide whether to start the fixed fire extinguishing system. Although there are automatic and manual start-up modes in the design, manual start-up mode should be the main one when someone is on duty.
So the fire control center panel only displays the manual automatic working state of the system. It monitors the system of alarm and injecting feedback signals at various stages, and controls other linkage devices such as fireproof doors and windows, air conditioning and fireproof valves. But it is not required to immediately start off the fire extinguishing system. This is to ensure the reliability and accuracy of the system.
Electric Fire and Electric Socket
May 01, 2018 Brazil São Paulo fire caused high rising building collapses in huge blaze. The public security bureau said the fire was caused by short circuit of a electric socket.
Which electric device on fire is the most dangerous? Computer? TV set? No, it is electric socket. About 30% fire is caused by electric socket. Incorrect selecting of the electric socket, improper installing or using of the electric socket may cause fire. Below are the details.
1.The electric socket is mounted too low and near the floor.
If the electric socket is mounted lower and near the floor, the water will easy splash into the electric socket when you mop the floor. That will cause short circuit of the electric socket.
2.No water proof cover is installed for electric sockets in kitchen room and bathrooms. The water will easy splash into the electric socket when you wash the dishes in kitchen rooms and taking shower in bathroom.
3.A few electrical appliances share a socket. The socket may be burn out and cause fire because of excessive power.
4.Aluminum wire is used as power line.
Aluminum wire is easy to oxidize, and the joint part is easy to strike fire. So, copper wire is needed for power line. The switch should be connected to live wire.
5.Change the place of earth wire.
The earth wire should not be placed randomly. Earth wire can protect us when electric leakage occur for house appliance.
6.Only one circuit for all house appliance.
If one house appliance is short circuit, then all house appliance will be burned out. The best one is one room one circuit especially bathroom and kitchen room.
7.Universal socket is used.
The universal socket jack is too large and the contact area between socket connector and electrical appliance plug is too small. It is easy to overheat the contact sheet and cause a fire.
Combustible gas leakage disposing
Natural gas, LPG is used for home cooking, heating. But the gas is with dangers if it is not used properly. So, people should know how to use the gas source correctly. A gas detector is not enough for home gas security. A connected solenoid valve is better for gas source leakage shut off.
What should we do if gas leakage is detected? The fire fighting person said:”When we are at gas leakage spot, we even dare not kick the door or knock, smash with a metal tool. Because that may produce spark and detonate gas.” We should remember what we must not do at gas leakage spot.
1.No fire is allowed, no smoking, no lighter. Otherwise the leakage gas make be detonated.
2.No turning on/off of house appliance. Because that may produce spark and detonate gas.
3.Do not dial telephone at gas leakage spot. Because that may produce spark and detonate gas.
What should we do then when we find gas leakage?
1.Shut off gas source. Tighten the LPG bottle valve. Open the doors and windows for ventilation. Can use a broom to disperse gas leakage in air.
2.If the LPG bottle is with cracks, it should be gently moved to the outdoor ventilation place.
3.If large amount gas leakage is found, please leave the spot immediately. Cut off the power supply. Extinguish all fire. Go outdoor and call for help.
4.If gas leakage is found from neighbor home, please knock the door to notice it. Do not press the door bell.
Explosion proof Fire Alarm Gas Detector Sounder Beacon
Explosion proof products are required to be used in oil field, chemical industry factory, metallurgical industry environment. Harmful gas detector, sounder, siren strobe, beacon, fire alarm systems are used for these fields with explosion proof requirement. That is because there is explosive mixture in these environment.
There are three types explosion proof products: intrinsically safe type, flameproof type, increased safety types.
Explosion Proof zones:
zone 0: Under normal circumstances, explosive gas mixture exists continuously or for a long time.
zone 1: Potentially explosive gas mixtures may exist under normal conditions
zone 2: Under normal circumstances explosive gas mixtures does not exist, only in abnormal situations, explosive gas mixtures
may exist occasionally or in short-time.
zone 10: Under normal circumstances, the mixture of explosive dust or combustible fiber and air may exist continuously, appear frequently or exist for a long time.
zone 11: Explosive dust or mixtures of combustible fibres and air cannot occur, only occur in occasionally or for short periods in unusual circumstances.
According to explosion gas species and Minimum detonation spark energy, the gas explosion is divided into 4 grade.
According to explosion gas temperature, there are 6 groups. Check below of temperature groups and gas species.
Explosion-proof certification mark
According to factory or mine explosion media, the minimum sparking energy, the minimum sparking temperature and explosion gas existing time, there is classification of explosion proof certification mark.
For example: ATEX form, E Ex iaIIC T4, E means Cenlecom certificate mark, Ex means explosion proof, ia means intrinsically safe type and can be installed at zone 0 area. IIC means it can be used at environment where IIC type gas exists. T4 means it meets T4 safety temperature group requirement.
Dust and water proof grade:
Explosion proof products have dust and water proof capacity as well. It is marked as IPXX. For example: IP65 means it has totally dust resistance capacity and can accept low pressure water jet from all angles.
Vedard Security supplies explosion proof sounder, bell and lighting, siren strobe, smoke detector, heat detector, H2S detector explosion proof, beacon explosion proof, HC detector, manual call point explosion proof.
The explosion proof detectors and alarms can be connected to fire alarm control panel, manual call point. The detectors are installed at chemistry factory, mines.
Fire Alarm System Troubles Resolve Solutions
Fire alarm system is professional security equipment. Different fire security equipment manufacturer has different design coding and programming methods. But general fire alarm system design and functions are similar. Below we will list some troubles and resolve solutions for the fire alarm system programming and operation.
1. Fire Bell, Siren strobe does not react when fire alarm is triggered.
Solutions:
A.Please check whether or not the indication LED is on.
B.Please check whether or not there is fault information of the fire bell, siren strobe on the fire alarm control panel.
C.Please check whether or not 24V power is supplied for the fire bell, siren strobe.
D.Please check whether or not the fire bell control module is set as remote sound or siren strobe
E.Please check whether or not the output of fire bell, siren strobe is active on linkage setting.
2. When fire alarm is triggered, some equipment has requested reaction, but there is no reaction from on spot equipment, why?
Solution:
The equipment feedback signal should be sent by control surveillance module. So, please check whether or not the on spot equipment status is set as automatic and can be turned on by control module. If it is set as automatic, then check the feedback signal wiring and make sure it is wired well.
3. Some circuit keeps reporting fault or feedback and then disappears automatically, why?
Solution:
The caution is equipment type is not compatible or there is strong interference from the circuit. If using menu operation to test the point, the waving can be seen from the diagram curve. Generally it is cause of bad connection between circuit signal GND with earth. Please measure the resistor of the GND circuit and at normal it should be more than 5mω.
4. Some circuit can only trigger alarm linkage once, after that no fire alarm or feedback can be activated, why?
Solution: There is short circuit between detector or module circuit with control module. So, please check the circuit.
5. The fire alarm control panel reports main power fault and backup power fault as well?
A.Please check and make sure the main power feedback wire is well connected.
B.Please check and make sure the alarm panel power setting of power feedback type is the type of actual used power.
6. What fault can be isolated and what fault can not be isolated?
When pressing the isolate key on the fire alarm panel, it can isolates all detectors and modules which are triggering alarms. From menu setting of detectors and modules, the isolation function can isolate detectors and modules on this machine only.
The isolation function can not isolate system fault such as panel communication fault, panel power fault, interface communication fault or circuit fault, printing fault, repeat display fault etc.
7. There is no fire alarm or fault alarm report from fire alarm control panel, but the detector or module inspection indication LED is flashing.
Solutions: Maybe there is interference signal on the circuit. Please disconnect the circuit, then connect part of the circuit to system and test, repeat doing it till problem is found.
Maybe there is module or detector positive and negative polarity reversal. Please remove the circuit from the alarm panel and measure the resistor of positive phase and reverse phase.