Fire is a great servant but a bad master. Rightly said because as fire is in its incipient stage it may be brought under control but once it gets out of control it becomes very difficult to save life and property that it may have taken under its control. Thus first let us understand what fire is!

This article has been divided into 8 parts:

1. What is Fire?

2. Principles to extinguish fire

3. Why do we need to understand classes of fire?

4. Classes of Fire

5. Stages of Fire

6. Choice of Fire Extinguishers

7. How to respond to fire in incipient stage using a Fire Extinguisher

8. Conclusion

1. What is Fire?

Fire is a rapid chemical reaction of oxidant with fuel accompanied by the release of energy, indicated by incandescence or flame.

Thus this suggests that to have fire we must have 3 ingredients that are:

  1. Fuel : Any combustible material such as: solid, liquid, or gas. Eg: Wood, Petrol, Oil Gas etc.
  2. Oxygen : Sufficient oxygen must be present in the atmosphere surrounding the fuel for fire to burn.
  3. Heat : Sufficient heat energy must be applied to raise the fuel to it’s ignition temperature. Sources of heat are – Naked flame, Hot surfaces, Sparks, Friction etc.
The Fire Triangle

The absense of any of the three elements will result in fire to get extinguished. Chemical chain reactions keep the fire burning.

2. Principles to extinguish fire

Thus we may infer from the above section that there are basically 3 methods to extinguish fire which are:

  1. Cutting off Fuel – Starvation
  2. Cutting off Oxygen – Smothering
  3. Cutting off Heat – Cooling
The Fire Triangle

3. Why do we need to understand classes of fire?

Do you remember the experiment performed by Rancho in the movie “3 idiots” where he proved that salt water is a great conductor of electricity?

Well so it is very easy to infer that we will not be using a water type extinguisher on any kind of electrical fire.

Thus basically to understand what kind of an extinguishing media needs to be used to extinguish fires of various types we have classified fire into 5 categories.

4. Classes of Fire

  • Class A – fires involving solid materials such as wood, paper or textiles.
  • Class B – fires involving flammable liquids such as petrol, diesel or oils.
  • Class C – fires involving gases or energized substances/ Cables.

Always class “C” fires is to be treated as though power is still on! Once the power has been removed, it can probably be treated like a Class A or B fire, but remember that cables & equipment can hold electricity even after the power is off!

  • Class D – fires involving metals e.g. Sodium, Potassium, Magnesium etc.
  • Class K – fires involving cooking oils such as in deep-fat fryers.

5. Stages of Fire

The action plan for responding to any fire related emergency depends on the stage of fire as well.

There are basically 4 stages of fire:

Incipient Stage :

The incipient stage is when it’s crucial to fight a fire because it is easiest to suppress it at this point, and it will cause the least damage. It’s difficult to manually fight and extinguish a fire when it is in this stage because of the time it takes to identify the fire, locate a handheld extinguisher, and perform the proper steps to spray the fire. Fire suppression systems help to suppress the fire right after ignition without needing a person to be present.

• Growth stage :

Once a fire reaches this stage, it becomes harder to control. If a fire detector recognizes a fire at this point, one has little time to put it out before it reaches flashover.

Flashover may be defined as a transitional phase in the development of a compartment fire in which surfaces exposed to thermal radiation reach its ignition temperature more or less simultaneously and fire spreads rapidly throughout the space resulting in full room involvement or total involvement of the compartment or enclosed area.

• Fully developed stage :

A fully developed fire is the hardest to suppress because, at this point, the fire is at maximum temperatures and causing the most heat damage. If failed to suppress fire before this point, then odds of stopping the fire are much smaller.

Decay stage :

The decay of a fire is the phase when the fire decreases in intensity until it is either a smolder or non-existent. If there was no suppression, this is likely when there is nothing left for the fire to burn.

Stages of fire

It is anyone and everyone who can help inhibit the growth of fire from its incipient stage to fully developed stage. Thus now after having understood the classes of fire we can infer that based on the class of fire we are to use the extinguishing media most suitable to the class to inhibit the fire.

6. Choice of Fire Extinguishers

There are 5 main types of fire extinguishers:

  • Carbon Dioxide (‘CO2’)
  • Foam
  • Wet Chemical
  • Water, water mist or water spray
  • Dry Powder – standard or specialist

The images of typical fire extinguishers in the above order are as follows:

The ABCs, Ds, and Ks of Fire Extinguishers -- Occupational Health & Safety

The following image will help you to select the most suitable type of extinguisher:

Fire Extinguishers Fire Hose Fire Class ABC Dry Chemical Classification Of  Fires, PNG, 1200x700px, Fire Extinguishers,
What's Your Extinguisher Type? | Retiree News

7. How to respond to fire in incipient stage using a Fire Extinguisher

The following steps should be followed when responding to incipient stage fire:
  • Sound the fire alarm and call the fire department, if appropriate.
  • Identify a safe evacuation path before approaching the fire. Do not allow the fire, heat, or smoke to come between you and your evacuation path.
  • Select the appropriate type of extinguisher.
  • Discharge the extinguisher within its effective range using the P.A.S.S  technique (pull, aim, squeeze, sweep).
  • Back away from an extinguished fire in case it flames up again.
  • Evacuate immediately if the extinguisher is empty and the fire is not out.
  • Evacuate immediately if the fire progresses beyond the incipient stage.

Most fire extinguishers operate using the following P.A.S.S. technique:

  1. PULL : Pull the pin. This will also break the tamper seal.
  2. AIM : Aim low, pointing the extinguisher nozzle (or its horn or hose) at the base of the fire. NOTE: Do not touch the plastic discharge horn on CO2 extinguishers, it gets very cold and may damage skin.
  3. SQUEEZE : Squeeze the handle to release the extinguishing agent.
  4. SWEEP : Sweep from side to side at the base of the fire until it appears to be out. Watch the area. If the fire re-ignites, repeat steps 2 – 4.
How to Use a Fire Extinguisher | Spectrum Fire Protection Blog

If you have the slightest doubt about your ability to fight a fire EVACUATE IMMEDIATELY!

8. Conclusion

It takes just awareness and presence of mind to shift from “by standers to fire emergency” to “responders to fire emergency“.

Thus with proper knowledge of fire and its classes, we can save life and property that may be of large emotional and monetary value.

7 thoughts on “Being First Responders to Fire

  1. Excellent presentation on the subject. If this is used for trainees, practical difficulties and how to overcome each of them may also be included.
    Best wishes.

    1. Sir, could you please kindly help us with the topics which may be included. We will try to make a different chapter on the topic.
      Thank you for your feedback.

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