Fire extinguishers are one of the quickest responses to fire available to the home owner. Many fires that might otherwise consume a home can be put out with a fire extinguisher before they ever manage to take hold and cause serious damage.
All fire extinguishers are not the same, however, and care should be taken to choose the correct model for your home.
Fire Extinguishers – How They Work
A fire needs oxygen to burn, deprive it of its oxygen and it dies. By expelling an oxygen limiting compound under pressure and blanketing the fire, this is exactly what a fire extinguisher does.
The compounds used, though, vary and some can have disastrous consequences if used on the wrong type of fire.
New Zealand Fire Extinguisher Classifications
The following list details the different classifications of fire extinguisher available in New Zealand. Each classification is marked with an alphabetical code.
- A – for use on ordinary combustible material e.g. paper, wood and many plastics.
- B – flammable liquids e.g. petrol, kerosene.
- C – flammable gas.
- D – combustible metals e.g. magnesium, sodium, potassium. Generally for specialised or laboratory use only.
- E – fires involving electrical equipment.
- F – cooking oil fires.
It is essential that the classification match the fire. Using a type A fire extinguisher, for instance, which may contain a water-based compound, could result in electrocution if used on an electrical fire.
Types of Fire Extinguisher
Broadly speaking, there are three types of fire extinguisher, divided by which oxygen depriving compound they use.
Water or Foam Fire Extinguishers
Generally suitable only for class A fires, water extinguishers expel water mixed with a foaming agent. The resulting foam smothers the fire. The electrical conductivity of water makes these extinguishers unsuitable on class E fires. Water/foam extinguishers should also not be used on burning liquids or oils as their powerful jet of water will displace the liquid and spread the fire.
Dry Chemical Fire Extinguishers
There are a number of varieties of dry chemical extinguishers, but all of them expel a powder that smothers fire. They are suitable for A, B and E fires and as such can be a versatile addition to the home fire fighting arsenal. Their downside is that they leave a mildly corrosive residue that may be damaging to electrical equipment.
Carbon Dioxide Fire Extinguishers
By displacing oxygen with a powerful jet of carbon dioxide, these extinguishers rob fire of the air it needs to continue burning. As carbon dioxide is a gas it leaves no residue and so will not harm electrical equipment.
Carbon dioxide extinguishers are a great choice for electrical fires, but may spread burning liquids and may also prove inadequate to deal with larger class A fires.
When choosing a fire extinguisher you will also see a numerical rating, usually preceding the alphabetical rating e.g. 9A. The number shows the relative capability of the extinguisher – the higher the number, the larger the fire it will be able to deal with.
As fire extinguishers are limited in the type of fires they can deal with it is important to identify the type of fire you are most at risk of and buy the appropriate extinguisher.
Kept where they are easily accessible in the kitchen, garage and workshop, the right fire extinguishers can literally be the difference between life and death.How to Choose a Fire Extinguisher,
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