Types of fire extinguisher

Water Fire Extinguishers:
The cheapest and most widely used fire extinguishers. Used for Class A fires. Not suitable for Class B (Liquid) fires, or where electricity is involved.

Foam Fire Extinguishers:
More expensive than water, but more versatile. Used for Classes A & B fires. Foam spray extinguishers are not recommended for fires involving electricity, but are safer than water if inadvertently sprayed onto live electrical apparatus. 

Dry Powder Fire Extinguishers:
Often termed the ‘multi-purpose’ extinguisher, as it can be used on classes A, B & C fires. Best for running liquid fires (Class B). Will efficiently extinguish Class C gas fires, BUT BEWARE, IT CAN BE DANGEROUS TO EXTINGUISH A GAS FIRE WITHOUT FIRST ISOLATING THE GAS SUPPLY.  Special powders are available for class D metal fires.

Warning: when used indoors, powder can obscure vision or damage goods and machinery. It is also very messy.

CO2 Fire Extinguishers:
Carbon Dioxide is ideal for fires involving electrical apparatus, and will also extinguish class B liquid fires, but has NO POST FIRE SECURITY and the fire could re-ignite.

Wet chemical
Specialist extinguisher for class K fires.

For Metal Fires: A specialist fire extinguisher for use on Class D fires - metal fires such as sodium, lithium, manganese and aluminium when in the form of swarf or turnings.

Colour Coding

Prior to 1st Jan 1997, the code of practice for fire extinguishers in the UK was BS 5423, which advised the colour coding of fire extinguishers as follows:

Water - Red

Foam - Cream

Dry Powder - Blue

Carbon Dioxide (CO2) - Black

Halon - Green (now 'illegal' except for a few exceptions such as the Police, Armed Services and Aircraft).

New extinguishers should conform to BS EN 3, which requires that the entire body of the extinguisher be coloured red. A zone of colour of up to 5% of the external area can be used to identify the contents using the old colour coding shown above.