The first modern fire extinguisher was invented by British sailor George William Manby in 1818, and worked by expelling potassium carbonate over the flames using compressed air. Although technology has moved on since then, these days fire extinguishers still remain the best way of preventing low-level conflagrations from endangering employees and destroying equipment by spreading.
One of the ways their design has advanced is that there are now different types of fire extinguisher for each potential source of fire. What each one contains is colour-coded on the outside; older ones tend to have their entire bodies painted in the corresponding colour, whilst new ones are usually red all over apart from an area near the instructions which displays it. The different types are:
Only used for Class A fires
Can be used from a distance
Heavy for users
Not suitable for use on electrical equipment
Water with additives
Used for Class A fires and Class B ones if indicated by the manufacturer
Lighter and more efficient than conventional water extinguishers
Used for Class A and Class B fires
Particularly effective against ignitable liquids such as petrol and diesel
Unsuitable against free-flowing liquids, or deep-fat fryer and chip pan fires
Used for most classes of fire
Good at compressing flames to halt spreading
Use on electrical fires likely to make the affected equipment useless
Lack of cooling means fires can re-ignite
May create loss of visibility and affect people with breathing difficulties
Unsuitable for use in enclosed spaces
Used for Class A and Class B fires
Can extinguish electrical fires without causing further equipment damage (apart from with very delicate machinery, such as computers)
Used only for Class F fires; those involving fryers and chip pans
The Regulatory Reform (Fire Safety) Order 2005 government regulations suggest that an office has one water-based fire extinguisher for every 200 square metres of floor space, with a minimum of two on each level of the building, and additional ones for other types of fire depending on their likelihood. They go on to say that no one should have to travel more than 30m to reach an extinguisher in the event of a fire, and they should be strategically located around escape routes, such as an exit from either the room or floor of the building. It's illegal for an office to have its extinguishers serviced less frequently than once a year.
Directions for Use
The various types of fire extinguisher each need to be handled slightly differently depending on what they contain; ones that have water, for example, are heavier than if they contain carbon dioxide, and so lifting them to aim at the base of the fire is more difficult. Something that's very important to remember is that any extinguisher typically has just enough content to last for ten seconds of use, so it's vital that the operator doesn't waste any by aiming away from the fire.
When using the extinguisher there are five important things to remember:
Remove the pin: This holds in place a locking mechanism that prevents its contents from being discharged.
Aim down: The fire will only go out if the fuel is extinguished, so its base needs to be aimed at rather than the flames.
Keep squeezing: The extinguishing agent will only continue to be expelled from the nozzle whilst someone holds down its handle.
Spray side-to-side: The extinguisher should be aimed back and forth across the ignited area until it has gone out.
Maintain the right distance: The different types of extinguisher mentioned above each have their own optimal distance for the user to stand away from the flames with them. However, regardless of what this is, it should be considered a starting point after which the user moves towards the flames once they've begun to die down.
As employers have a legal requirement to ensure the fire safety of their premises and staff it is in their interest to provide fire extinguisher training for them. The London Fire Brigade provides a half-day course that takes place on clients' premises, training employees in how to use the types of extinguisher that have been installed there.