We have seen the four stages of fire ie The Incipient, The Growth, The Fully Developed and The Decay in my last blog. In this blog let us understand the methods of fire fighting so that we can put out the fire and also understand the ways in which fire spreads from one place to the other.

Based on the fire triangle that we have studied, fire extinction can be done by removing any one element from the triangle consisting of Fuel, Oxygen and Heat. These 3 ways are called Starvation, Blanketing or Smothering and Cooling.

Starvation : It is the method of removing the Fuel element from the fire triangle. In this method the materials surrounding the area near the seat of fire are removed and the fire is made to starve without the supply of fuel. As the fire feeds on fuel when this is removed the fire does not get anything to burn and hence dies out by itself. This method of fire fighting is usually adopted by the fire fighters putting out fires which happen in homes with thatched roof. Not only do they pour water on the roof that is burning but they remove the thatched roofs from the nearby houses to contain the fire.

Blanketing/Smothering : In this method the oxygen supply to the fire is cut off. Naturally the fire is put off due to the lack of oxygen. I know many of us will remember our science lab in school where the teacher used to cover a lit candle, with a glass and show us the lack of oxygen. This method of putting out fire is also the same. It is a well known fact that human beings can survive without oxygen beyond 5 minutes but Fire cannot survive without oxygen even for a few seconds. The cutting off of oxygen supply can be done in homes by closing the doors and windows to the room which has caught fire, and also by using materials like blankets and wet towels when oil pans catch fire in the kitchen. If an oil pan catches fire in the kitchen the same can be put out by first switching off the gas supply and then covering the pan with a wet cloth or blanket. Even some of the fire extinguishers use this method to put out fires.

Cooling : In this method the heat element is simply removed from the fire. This can be done by using water over the fire as water is a great absorber of heat. Water can be used on solid fuels like paper, coal, leaves etc but cannot be used on flammable liquids, gases and electrical fires. On fire where you cannot pour water directly the water can be used in areas adjacent to the fire to cool the heat and not allowing the fire to spread. The firemen use this method most often in fires in buildings and homes.

Fire Spread happens due to transfer of heat and the methods of heat transfer are Conduction, Convection and Radiation. We shall discuss these methods in my next blog.

As the festival of lights DIWALI, is fast approaching just wanted to give my readers a few Safety Tips.

1. Burst Fireworks in open areas only.
2. Do not wear synthetic clothing while lighting fireworks.
3. Keep 2 buckets of water near the place where you light fireworks to render any first aid for fire burn.
4. Parents should supervise children when lighting fireworks.
5. Wear tight clothes rather than loose ones while lighting fireworks.
6. While lighting crackers ensure a safe distance between the body and the crackers.
7. Do not get too close to any misfired Crackers.
8. Always store the fireworks in a safe place well away from sources of heat.
9. Buy Fireworks from reputed manufacturers only.

For many Indians Diwali is a festival which brings in a lot of prosperity and joy in lives. Enjoy the festival by meeting and greeting your friends and loved ones but at the same time be careful with fireworks.

WISHING ALL MY READERS A VERY HAPPY DIWALI/DEEPAVALI.

Till my next blog be safe and stay safe.

Seshadri Varadrajan,
Sr. Corporate Trainer.
Usha fire Safety Equipments Pvt Ltd.
Chennai.

Call: 9840814353.
Email seshadri3225@gmail.com

Till now we have focused on what causes fire, its prevention, timely evacuation and LPG safety in the previous blogs. In this blog, the attention will be on the various stages of Fire and the way it spreads. Only when we know these aspects, it will help us not only to fight the fire but also do timely Evacuation. Normally we all use the words Small Fire or Big Fire. However technically there is no such thing as small fire or large fire it only fire in various stages.

As you all know, by now Fire is the rapid oxidation of material in a process of combustion, releasing heat and light and various reaction products. Basically, there are 4 stages of fire and they are Incipient, Growth, Fully developed, and Decay stage.

The Incipient Stage: This first stage begins when Fuel, Oxygen and Heat combine and have a chemical reaction called Combustion, resulting in a fire.  This is also known as Ignition stage and in this stage there will be a Flame and a little heat but no Fire. Usually in this stage the fire goes out on its own but if there are fuel sources around then it starts to feed on that and increase. In this stage the fire can be easily put out or suppressed and easy to evacuate. Here one needs to just raise the alarm and can fight the fire if trained to do so.

The Growth Stage: The growth stage is where the structures, fire load and oxygen are used to fuel the fire. In this stage there is flame, fire and extensive heat. There are numerous factors affecting the Growth of fire including where the fire started, what combustible materials are near it, ceiling height and the potential for ”Thermal Layering”. It is in this stage which is very short where a deadly phenomenon called “Flashover” happens thereby trapping, injuring or potentially killing people. In this stage one needs to Raise the alarm, evacuate the persons in the area and call the Fire Brigade. You can fight the fire if you are trained and confident to do so.

The Fully Developed Stage: When the growth stage has reached its max and all the combustible materials have been ignited, a fire is considered fully developed. This is the hottest stage of fire and can be deadly for anyone trapped within the fire areas. In this stage one can hardly do anything. It is foolish to go inside and try to rescue anyone trapped. Leave that work to the Professional Fire fighters. Even they cannot do anything but douse the fire. In the previous two stages damage to property is limited but in this stage the damage is very high.

 The Decay stage: Usually this is the longest stage of a fire, the decay stage is characterised by a significant decrease in oxygen or fuel, putting an end to the fire. Two common dangers during this stage are first—the existence of non flaming combustibles, which can potentially start a new fire when not fully extinguished and Second, there is a danger of a back draft when oxygen is reintroduced into a volatile confined space. In this stage one needs to be careful while opening the doors and also make sure the fire is extinguished completely.

While describing the four stages i have used the terms Flashover and Back draft. Let us now understand the definitions.

Flashover:  A flashover is the near-simultaneous ignition of most of the directly exposed combustible material in an enclosed area. When certain organic materials are heated, they undergo thermal decomposition and release flammable gases.

An example of flashover is ignition of a piece of furniture in a domestic room. The fire involving the initial piece of furniture can produce a layer of hot smoke which spreads across the ceiling in the room. The hot buoyant smoke layer grows in depth, as it is bounded by the walls of the room. The radiated heat from this layer heats the surfaces of the directly exposed combustible materials in the room, causing them to give off flammable gases via pyrolysis. When the temperatures of the evolved gases become high enough, these gases will ignite throughout their extent.

Back Draft pronounced as Back Draught: A back draft is a rapid or explosive burning of superheated gases in a fire, caused when oxygen rapidly enters an oxygen-depleted environment; for example, when a window or door to an enclosed space is opened or broken. Back drafts present a serious threat to fire fighters.

As these blogs are written for the benefit of everyone I will not be too technical though the subject of fire and fire fighting is highly technical.

We shall talk about the spread of Fire and how to put fire out in my next blog.

Stay safe, Be Safe and live happily.

Comments can now be posted on the blog page itself.

V.Seshadri
SR. Corporate trainer,
Usha Fire Safety Equipments private ltd, Chennai.
9840814353. Email: seshadri3225@gmail.com