Fire-proofing a building is extremely important since every year, thousands of buildings are lost to fire accidents. Taking a few steps during the design of your buildings may help prevent severe hazards.
There are two types of fire fighting systems:
- Active fire fighting system
- Passive fire fighting system
Active fire fighting systems are further available in many types and forms.
- Fire detection systems
- Fire suppression systems
- Oxygen reduction systems
- Ventilation systems
Fire Detection Systems
As the name suggests, fire detection systems help to immediately detect fire and alert the people/ authorities.
The most common type of notification device is the fire alarm. There are three components: initiating device, notification device and control panel.
A) Manual Initiating Device
- Manual fire alarm is a glass cased box which has a handle to make the alarm goes off.
- This device is activated when a person pulls the handle.
- Hence, this device must be placed in a place where it is visible and can be easily accessed.
B) Automatic Initiating Device
Automatic initiating devices detect fire using detectors like smoke and heat.
- These detectors set off when there is a sudden fluctuation in temperature or when heat suddenly increases.
- Since these detectors solely rely on increase in temperature, the rate of detection is relatively slower.
- False alarms are extremely rare.
- Cost is lower in comparison.
- These detectors detect smoke particles.
- Since smoke rises faster than heat, these detectors are fast.
- More expensive than heat detectors.
- Ideal for small spaces.
Radiant Energy Sensing Detectors
- These detectors monitor ultraviolet and infrared rays to detect fire.
Gas Sensing Detectors
- This detector senses gas and vapour particles.
- Gas sensing detectors are usually used in high hazard areas like oil rigs and wells, HVAC units etc.
Fire Suppression System
In case of fire breaking out, the fire suppression systems immediately activate to keep the fire from spreading.
A) Fire Extinguishers
Fire extinguishers are manually operated cylindrical devices which help in controlling small fires.
Class A Fire Extinguishers
- These extinguishers are used to extinguish common fires fueled by paper or wood.
- Usually clean agents or water mist is used.
Class B Fire Extinguishers
- Class B fire extinguishers are used for use on flammable liquids like grease, gasoline, and oil.
- These often use C02 or clean agents to suppress fires.
- They leave no residue behind.
Class C Fire Extinguishers
- Class C fire extinguishers are used on fires that are electrically energized.
- Most class C fire extinguishers use CO2 or similar clean agents to suppress fire, without adding any conductive materials to the flames.
Class D Fire Extinguishers
- Class D fire extinguishers are used on combustible metals like magnesium and titanium.
- These use a dry powder agent to stop the fire and absorb heat, thereby suppressing the fire.
- These agents should not react with the burning metal.
Class K Fire Extinguishers
- Class K fire extinguishers are made to combat kitchen fires.
- This type is effective on cooking fat, grease, and oil fires.
- They usually employ a wet chemical agent composed of potassium to simultaneously cool and suppress the fire.
B) Sprinkler System
Sprinkler system has water under pressure in pipes along the ceiling in select locations. When a fire breaks out, the seal holding the water back ruptures and allows it to flow down. This prevents the fire from spreading, allowing more time for evacuation.
Wet Pipe System
- This system is the most commonly used sprinkler system.
- Water is constantly maintained under pressure in the pipes.
- When the temperature increases above a pre-established value, the head Burt's open to let the water out.
- Since the water is already present and is released almost immediately, the fire below is immediately extinguished.
Dry Pipe Sprinkler System
- Dry Pipe sprinkler system is used in areas that are prone to freezing.
- In dry pipe system, the pipes are empty and water fills up only when fire is detected.
- The water is held back by a valve when opens when pressure drops.
- In this system, the water takes about a minute to travel from the valve to the sprinkler head, making it a little slow.
- The pre-action system is very similar to the dry pipe system where the pipes are empty.
- The difference between the two is that, in dry pipe system, the valve opens when pressure drops, whereas the pre-action system has an electrically operated valve.
- The deluge system is used in high hazard places where fire spreads quickly.
- The pipes are empty in this system too, but they are directly connected to a designated water storage valve.
- Unlike the other systems, the sprinkler head in this system is always open, allowing it to dump large amount of water on the fire as soon as it is detected.
Oxygen Reduction Systems
These fire suppressing systems reduce the spread of fire by introducing inert gases like nitrogen to reduce the oxygen concentration below ignition threshold. Oxygen sensors are installed in the protected areas to continuously monitor the oxygen concentration until the fire is fully suppressed.
Active ventilation systems help disperse smoke and dust particles during a fire breakout using mechanical means like fans and exhausts. These devices assist in evacuation until the firefighters arrive.
A) Mechanical Ventilation/ Extraction Systems
- When good natural ventilation is limited, usage of mechanical systems like fans to push out smoke and draw fresh air in helps.
B) Smoke Control System
- Smoke Control system helps to avoid the spread of smoke during a fire.
C) Smoke Clearance System
- Smoke clearance system helps in dispersing smoke and ventilating the area after fire has been extinguished.
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