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Faqs

Subject: Smoke alarms
Q:1) Our smoke alarm seems too be sensitive. It goes to alarm several times a week. Can we do anything to make it less sensitive? Or could I buy a smoke alarm that is less sensitive? 
A: 1) How old is the detector? If it is more than 8 years old, replace the detector.
2) Are the detectors connected to an alarm panel? One easy, but a little more expensive, solution is to replace the ionization smoke detector with a photo smoke detector. 
The ionization smoke detector is the most common detector found in the home/offices. It is the most sensitive, giving you the fastest alarm notification. Best for smoldering fires. 
The photo smoke detector is a very stable detector, but requires a more "visual type" of smoke. 
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Subject: Auto Dialer
Q: What is an Auto Dialer? 
A:
Auto dialer is a part of the Fire Alarm system. An auto dialer, in an alarm condition automatically dials to the pre-stored phone nos and plays a pre recorded voice message. 
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Subject: Number of detectors.
Q: 1) How many smoke/heat detectors are allowed per zone on a conventional panel?
2) How many manual boxes are allowed per zone?
3) How big can a zone be in metres squared?
4) On an intelligent loop system panel how many devices are allowed and what is the maximum length of loop wiring allowed?
5) What is the difference between a line type detector and a spot type detector?

A: The number of detectors per zone is going to depend on the current draw of the smoke detectors (assuming a 2 wire smoke) and the type of the panel. Typically, no more than 30 devices per zone. As far as heat detectors or other contact devices such as pull stations, you could have an unlimited number per zone, but this is not recommended.
The size of a zone is / should be based on the structure of the building or the customers needs.
An addressable loop system will very with manufacturer. The length of the loop will also very greatly, based on resistance, capacitance, or inductance.
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Subject: Life of detectors.
Q: Do smoke detectors have a finite life?
A:
All equipment has a useful life.
There are two type of smoke detectors, ionization and photoelectric. 

Ionization type uses a small radioactive foil to create electrically conductive air molecules (ions) in a chamber.

The ions allow electricity to pass through the chamber. Smoke absorbs the ions and decreases the electrical flow.  A decrease in flow below a set point causes an alarm. As the radioactive foil ages, it does not produce as much ions in the air. This results in overly sensitive smoke detection. This is a failure that is "fail safe" rather than fail dangerous. Fail-safe leads to more false alarms.

Photoelectric types generally are the more expensive models of home smoke detectors. The ones made in the last 20 years use a LED to flash light into a dark chamber, there is a photocell watching the chamber at an angle to the LED. Only reflected light from smoke (or dust, steam, oil from cooking) can be seen by the photocell. This is not a "fail safe" arrangement, but LEDs have an extremely long life (100's of years) and are unlikely to burn out.

Both types of detectors can fail due to blocked vents on their detection chambers (from dust and dirt, spider webs). They also fail due to dead batteries (change your battery yearly) or loss of AC power.
It is most important to test the detector monthly. Replace when it fails or when it starts false alarming too much.
Replace smoke detectors every 10 years. There is not study that supports this. National codes do not force replacements; they only identify the need to test units regularly. If a bunch of smoke detectors start to fail in an industrial building, then the owner would probably replace all the units.
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Subject: Working principle of Detectors.

Q: How a photoelectric smoke detector, thermal detectors and manual pull stations work. All are conventional detectors connected to intelligent monitor modules and to an intelligent control panel.

A: The most common type of Photoelectric Smoke Detector works by emitting a "beam of light" in a darkened chamber.

When smoke passes through the chamber, some of the light is "bounced" off of the smoke and reflected back into a receiver. Depending on how much light is reflected back, will determine the "Alarm Point". When the Alarm Point is reached, a set of contacts is closed.
Thermal Detectors also come in a few different types; the most common is the Rate Of Rise and Fixed Temperature type. Most rate of rise detectors use a bi-metallic strip to sense the change in temperature. As the temperature changes, the two different types of metal expand and contract at different rates. The faster the rise in temperature, approx 15 to 20 degrees/min., will cause the metal to touch, thus, causing an alarm. The fixed temp. Portion works by using a "solder like material" with a very low melting point. When the temp reaches the "alarm point", the "solder" melts and lets a spring push the "heat element" off of the detector and close a contact.
A Pull Station is just a switch. When you pull the lever, you are moving a switch inside the back of the pull station.
The modules just monitor the switches or contacts in the devices. When the switches "Close" then the modules transmit their device address to the control panel along with an alarm signal. Like wise, if the module can't "see the switch", it will send a trouble signal to the control panel.
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Subject: Design standards
Q: What are design standards for fire alarm and Gas based fire supression system
A: The different satandrards are as follows
NFPA 12 - Standard on Carbon Dioxide Extinguishing Systems
NFPA 13 - Standard for the Installation of Sprinkler Systems
NFPA 2001 - Standard on Clean Agent Fire Extinguishing Systems
IS 2189 - Code of practice for Slection, Installation & amintenance of Automatic Fire detection & Alrm System
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Subject: Clean Agent.
Q: What is clean agent.
A:
Clean agents are gaseous fire suppressing agents. Because they suppress fire as gases, there is no damage to protected areas from the discharge and no residue to clean up. Thus, the term "clean" agents.
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Subject: Clean Agent use
Q: Where Clean agent are used.
A:
The clean agent fire suppression system are better options to protect highly valuable are protected areas. Clean agents not only protect the area but they protect the contents in the protected areas including the people, documents & equipments. The early protection, minimum damage to equipments and safety of the people are the main advantages of clean agent suppression systems. The clean agent (gases) used gives an ability to enter in to cabinets & obstructed areas which protects the hidden electronic components inside a control panel. Also the agent can be easily ventilated from the room after the fire is extinguished.

Unlike water Clean agents are non-conductive, non-corrosive, non-residue to clean-up. The equipments in protected area are brought back to on-line and productive quickly.

The increased sophisticated electronics, telecommunications and other valuable equipment, requires protection as effectively as possible. Clean agent systems are the best way to keep critical operations running.
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Subject: Types of Clean Agents
Q: Where Clean agent are used.
A:
The three commercially-available clean agents for total flooding applications are INERGEN - manufactured by Ansul, FM-200 - manufactured by Great Lakes Chemical Company, and FE-13, manufactured by Dupoint.
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Subject: Fire Classification
Q: Which are different classes of fire.
A:
The material that burns in fires varies greatly. Similarly, the equipment used to extinguish fires varies. To properly identify different fire types, a method of classifying fire exists. Fire classifications will determine what type of agent should be used to most effectively and safely extinguish the fire.
Class A Fire: ordinary combustibles, wood, paper, textiles, etc.
Class B Fire: flammable liquids, gasoline, oils, fats, etc.
Class C Fire: live electrical wiring, motors, appliances, etc.
Class D Fire—combustible metals, magnesium, potassium, etc.
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Subject: Fire Detectors
Q: What are different types of Fire Detectors.
A:
The three most common types of fire detectors are: smoke detectors, heat detectors and flame detectors.
Heat Detectors
Heat detectors are used in dirty environments or places where dense smoke is produced. Heat detectors may be less sensitive when compared to smoke detectors, but are more appropriate than a smoke detector in these environments. The most common heat detectors either reacts to a broad temperature change or a predetermined fixed temperature.
Smoke detectors
The role of smoke detectors is to detect the visible or invisible smoke particles from combustion. The two main types of smoke detectors in use are ionization detectors and photoelectric detectors. The ionization detector contains a small radioactive source that is used to charge the air inside a small chamber. The charged air allows a small current to cross through the chamber and complete an electrical circuit. When smoke enters the chamber, it shields the radiation, which stops the current and triggers an alarm.
In the photoelectric smoke detector, a light source and light sensor are arranged in such a way that the rays from the light source do not hit the light sensor. When smoke particles enter the light path, some of the light is scattered and redirected onto the sensor, causing the detector to activate an alarm.
Flame Detectors
Flame detectors are line-of-sight devices that look for specific types of light including infrared, visible, and ultraviolet, emitted by flames during combustion. When the detector recognizes this light from a fire, it sends a signal to activate an alarm.
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Subject: Suppression methods
Q: Which are different methods of fire suppression
A:
Five Types of Fire and Their Suppression Methods

Fire Class Type of Fire Elements of Fire Suppression Method
A Common combustibles Wood and Paper Water, Soda acid or Gas (FM-200)
B Liquid Petroleum and coolants Gas (FM 200), CO2 or Soda Acid
C Electrical Electrical Gas (FM 200), CO2
D Combustible Magnesium, Sodium Dry Powder
K Cooking materials Grease, Oil, Food Water, Dry Powder

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Subject: Replacing a detector.
Q: If a detector is to be replaced. Can one disconnect it and replace it without having the alarm.?
A:
The short answer is "yes." The detectors signal an alarm to a closed circuit; disconnecting wires (an open circuit) create a trouble/fault condition. As long as you don't inadvertently short the wires during replacement, you can replace it in working condition.
If the control panel has the provision for isolating the zone (which normally every type of panel has) then you can isolate it before replacing the same.
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Subject: Smoke alarms
Q: Our smoke alarm seems too be sensitive. It goes to alarm several times a week. Can we do anything to make it less sensitive? Or could I buy a smoke alarm that is less sensitive?
A:
1) How old is the detector? If it is more than 8 years old, replace the detector.
2) Are the detectors connected to an alarm panel? One easy, but a little more expensive, solution is to replace the ionization smoke detector with a photo smoke detector.
The ionization smoke detector is the most common detector found in the home/offices. It is the most sensitive, giving you the fastest alarm notification. Best for smoldering fires.
The photo smoke detector is a very stable detector, but requires a more "visual type" of smoke.
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Subject: Auto Dialer
Q: What is an Auto Dialer?
A:
Auto dialer is a part of the Fire Alarm system. An auto dialer, in an alarm condition automatically dials to the pre-stored phone nos and plays a pre recorded voice message. This devise is very useful where an telephone connection is available at control panel. Use of auto dialer eliminates the repeater panel and necessary cabling required for it.
--------------------------------------------------------------------------------If you have any queries please mail to us.
E-mail : teisen@vsnl.com / teisenfire@yahoo.co.uk