FIRE SAFETY
The Fire Triangle
In order to understand how fire extinguishers work, you first need to know a little about fire
Oxygen, heat, and fuel are frequently referred to as the “fire triangle.” Add in the fourth element, the chemical reaction, and you actually have a fire. The important thing to remember is: take any of these four things away, and the fire will be extinguished.
Four things must be present at the same time to produce fire:
- Enough oxygen to sustain combustion
- Enough heat to raise the material to its ignition temperature
- Some sort of fuel or combustible material, and
- The chemical, exothermic reaction that is fire.
Take a look at the diagram, called the “Fire Triangle”
Fire Triangle
Essentially, fire extinguishers put out the fire by taking away one or more elements of the fire triangle. Fire safety at its most basic is based on the principle of keeping fuel and ignition sources separate.
Classifications of Fuel
Not all fuels are the same, and if you use the wrong type of fire extinguisher on the wrong type of fuel, you can, in fact, make things much worse. It is therefore very important to understand the four different calssifications of fuel.
Class A
Solid Combustible Materials i.e. Paper, Wood, Rubbish, Textiles.
Class B
Flammable Liquids i.e. Petrol, Diesel, Oil.
Class C
Flammable Gases i.e. Natural Gas, Propane.
Class D
Combustible Metals i.e. Sodium, Potassium, Lithium.
Class F
Cooking Oils/Fats i.e. Deep Fat Fryers.
Class E*
Electrical Fires i.e. Short Circuiting Equipment.
*Class E doesn’t technically exist because electricity is a source of ignition rather than a fuel. However, electrical fires can electrocute those using an incorrect fire extinguisher and these types of fires require special attention.
Note: Once the electricity supply has been turned off, the fire can be categorized into one of the classes above depending on the source of fuel.
Types of Fire Extinguisher
Portable fire extinguishers must conform to BS EN3 Standard, which specifies that their body is coloured red. A small coloured band indicates the type of fire extinguisher – red for water, white and red for water mist, cream for foam, blue for dry powder, yellow for wet chemical, green for clean agent and black for CO2 extinguishers.
Fire Blankets
Fire blankets are effective in smothering small, contained fires in kitchens or boats, if a good seal is made, and can also be used for wrapping around people whose clothing is on fire. Made of fiberglass, they can withstand temperatures of up to 500° C and are compact and portable. They don’t require maintenance as they can only be used once.
Using a Fire Extinguisher
The following steps should be followed when responding to incipient stage fire:
- Sound the fire alarm and call 999 if appropriate.
- Always 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 fire 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.
A joint survey into the use of portable fire extinguishers in the UK was recently undertaken by the Fire Extinguishing Trades Association (FETA) and the Independent Fire Engineering & Distributors Association (IFEDA).
According to the survey, fire extinguishers are estimated to:
- Save the UK economy over £500 million (based on values of the total fire claims
for commercial premises) - Have prevented 1,629 injuries (based on figures for deaths and injuries caused by fire)
- Prevent the loss of 24 lives (based on figures for deaths and injuries caused by fire)
Fire losses in the UK are currently estimated at £7 billion per annum but these
official statistics only take into account those incidents reported to the fire service.