It is important to use the appropriate extinguisher for the type of substance that is burning (wood, oil, electrics, etc.) as shown by the classification below. First of all you need to understand the different classes of fires.
Class A – a fire involving solid materials, usually of an organic nature, in which combustion normally takes place with the formation of glowing embers. Combustible materials include paper, wood, cardboard and most plastics.
Class B – a fire that involve flammable or combustible liquids such as petrol, kerosene, grease and oil.
Class C – a fire involving electrical equipment such as appliances, wiring, circuit breakers and outlets, or a class A, B or D fire occurring in the presence of energized electrical equipment. VERY IMPORTANT!! Never use water to extinguish class C fires!
Class D – a fire involving chemicals and combustible metals such as magnesium, titanium, potassium and sodium.
Class F – fires that involve cooking oils, trans-fats or fats in cooking appliances that are typically found in restaurants.
Different extinguishing mediums are available for specific classes of fire which necessitates the assessment of the type of hazard in the particular area you are protecting in order to maximise the effectiveness of the extinguisher you are going to have available in a fire emergency.
|EXTINGUISHING MEDIUM||FIRE CLASS|
S = Suitable
MS = Most Suitable
D = Dangerous
U = Unsuitable
LS = Less Suitable
- In most cases a combination of DCP (Powder ABC) and CO2 extinguishers will be sufficient to extinguish class A, B and C fires.
- CO2 extinguishers are most suitable for Class C fires. Carbon dioxide extinguishers work by displacing or taking away the oxygen element of the fire triangle. The carbon dioxide is also very cold as it comes out of the extinguisher, so it cools the fuel as well.
- Fire fighting foams contained in a foam extinguisher is an aerated solution which is used for fire prevention and firefighting. It is ideal for MULTI-RISK situations where both Class A combustible materials and Class B, flammable liquid/gases, are likely to be found, or where Class B risks represent a direct hazard. Foams have a low viscosity and will spread rapidly across the surface of most fuel based fires.
- Class D and F fires require specialised extinguishers.
- A specialised Class D fire extinguisher is recommended where there is a risk of Class D type fires.
- For Class F fires a wet chemical extinguisher is recommended and is ideal for restaurant and hotel kitchens. The medium contained in the extinguisher cools the fire and causes the hot oil to solidify. The medium is discharged as a fine spray which reduces the possibility of splashing hot oil.
- A purple K extinguisher is one of the most effective dry chemicals in fighting Class B (flammable liquid) fires and for use in areas such as airfields, chemical plants and refineries where superior fire extinguishing qualities are required. Purple-K powder should NEVER be mixed with phosphate-based fire suppression agents.
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