West Sussex Fire and Rescue Service FIRE EXTINGUISHER USE COURSE NOTES WEST SUSSEX FIRE AND RESCUE SERVICE

Transcription

1 FIRE EXTINGUISHER USE COURSE NOTES WEST SUSSEX FIRE AND RESCUE SERVICE

2 FIRE EXTINGUISHERS THE BASIC FACTORS OF COMBUSTION AND TYPES OF FIRE Basically, fire is a chemical reaction and three things are needed for it to take place, namely FUEL, HEAT and OXYGEN. OXYGEN HEAT Fuel, heat and oxygen form what is known as the fire triangle FUEL FUELS These are something to burn, and may be:- Solids: Liquids: Gases: Timber and coal are examples of normal solid fuel, but many other substances such as cotton, wool, celluloid, rubber and plastics can act as fuels Such as petrol, paraffin or diesel Such as domestic natural gas and butane gas HEAT AND IGNITION The actual process of combustion in the case of solids and liquids takes place in two stages, although with dusts and a thin substance like paper, the two stages seem to be almost instantaneous. The solid or liquid is heated to a temperature at which it gives off a vapour it is this vapour which is then ignited by the flame or spark. OXYGEN Combustion cannot usually take place without oxygen. This is in plentiful supply as it makes up a fifth of the air we breathe. Fuels vary in the proportion of oxygen required for burning.

3 BREAKING THE FIRE TRIANGLE Methods of extinguishing fire are based on the principle of removing one or more of the elements of the fire triangle. REMOVAL Removal or limitation of FUEL by removing combustible material from the neighbourhood of the fire. SMOTHERING OR THE LIMITING OF OXYGEN The principle of smothering can be used to snuff a candle, to cap a burning oil well and the battening down of a ship s hold will often hold flames in check until port is reached. Fires such as those involving a person s clothing can be smothered with a rug or blanket. Sand, earth, foam or finely divided particles of dry powder, usually sodium, bicarbonate, are also used to smother fires. COOLING The most effective method for removing HEAT from a fire is by cooling with water, giving the best results on solids.

4 SMOKE Smoke generated from fires is a collection of gases and vapours, ash, tar and soot particles, all of which give smoke its density and colour. There can be more than 25 different gases found in smoke that is given off when synthetic materials burn. Four of the more common gases that occur are:- Carbon Dioxide, Carbon Monoxide, Hydrogen Chloride and Hydrogen Cyanide Carbon Dioxide (CO 2 ) is not toxic but is an asphyxiant. In between 3% and 7% in our bodies, our breathing is stimulated. This is normal. Over 7% and we start to asphyxiate, by 10+% death will follow. Carbon Monoxide (CO) however, is toxic. CO chemically prevents our red blood cells from transporting oxygen from our lungs to our body tissue and carbon dioxide from our body tissue to our lungs to be exhaled. We become light-headed, dizzy, confused, disorientated, drowsy, unconscious then dead. It only takes 40 parts per million of CO in the air to have an effect 500 parts per million to kill. The physical effects are the slowing up and then seizing up of the muscles. Hydrogen Chloride (HCL) the gas form of Hydrochloric Acid forms the liquid acid when it comes into contact with moisture smoke, this leads to a stinging sensation as the liquid acid is produced. It requires only 80 pp, in the atmosphere to cause irreparable, irreversible damage to the respiratory system and possibly to the circulatory system. Hydrogen Chloride is produced when plastics containing chlorine are involved in fire. The plastics are the vinyls PVC is polyvinyl chloride Hydrogen Cyanide (HCn) is produced when plastics are involved in fire. The group of chemicals used as catalysts to produce plastics are the Isocyanates. When plastics are involved in fire the Isocyanates break down, and cyanide compounds are released into the smoke. Hydrogen Cyanide is the most common of these. HCn attacks the automatic nervous system it only takes ppm to have an affect, 40 ppm to kill

5 TYPES OF FIRE Class A fires involving solid materials, usually of an organic nature, in which combustion normally takes place with the formation of glowing embers Class B fires involving liquids or liquefiable solids Note: Class B fires are most efficiently extinguished by smothering. This may be done by using :- Dry powder An inert heavier than air gas e.g. carbon dioxide Foam that is a light aerated solution that floats on the surface of a burning liquid One of the modern vaporising liquids An incombustible blanket e.g. made of glass fibre Class C fires involving gases Note: No special provision can be made for dealing with fires involving gases because the only effective action against such a fire is to stop the flow of gas; indeed, there will be a risk of an explosion if a fire involving escaping gas is extinguished before the flow of gas has ceased. Class D fires involving metals Note: Special powders which are available for dealing with burning metals should be provided wherever there is a risk of fires involving such metals as magnesium, sodium and potassium.

6 FIRE EXTINGUISHERS In all premises to which fire safety legislation applies, there shall be provided and maintained appropriate means for fighting fires, which shall be so placed as to be readily available for use. RECOMMENDED STANDARDS OF FIREFIGHTING EQUIPMENT Published in Guides to the Fire Precautions Act 1971 Hotels and Boarding Houses, Factories, Offices, Shops and Railway Premises SITING OF EXTINGUISHERS The following recommendations are for what are described as normal fires, i.e. ordinary combustible materials such as wood, cloth and paper PORTABLE FIRE EXTINGUISHERS (WATER TYPE) If portable fire extinguishers are installed they should be provided in sufficient number to give adequate cover to those parts of the premises not covered by hose reels. One water type extinguisher of 9-litre capacity is normally sufficient for every 200 square metres or part thereof, with not less than 1 extinguisher on each floor. A double number of 4.5-litre capacity may be used. Extinguishers for normal risks should be placed in suitable positions throughout the premises. They should be mounted on brackets or shelves at a convenient height. Extinguishers for higher risks such as flammable liquids, petrol, oils, greases, fats and live electrical equipment should be immediately at hand, although care must be taken to place them so that they are not likely to become immediately unapproachable because of heat or smoke on the outbreak of fire. In some premises it may be necessary to site extinguishers where they are easily available to staff members and would not become obstructed by members of the public, e.g. behind counters in shops and departmental stores. Of course, care should be taken that they are suitable indicated and not obstructed by goods stored behind counters. New members of staff should be informed of the positions of the extinguishers and their use.

7 IDENTIFICATION A clear indication of the type of extinguisher, its limitations and method of operations should be given in a bold, legible notice near the extinguisher. RED BLUE CREAM BLACK WATER DRY POWDER FOAM CO2 FIRE BLANKET CLASS A CLASS B,C Some powders A CLASS A, B ELECTRICAL LIQUID FAT Class B REMEMBER Smoke will kill you only use an extinguisher if you feel confident and conditions allow. If you are breathing smoke GET OUT AND STAY OUT TOP TEN SAFETY TIPS How to make your house a safe home:- Fit a smoke alarm and check it regularly Make a fire action plan so everyone in your house knows how to escape in the event of a fire Take care when cooking with hot oil and think about using thermostatically controlled deep fat fryers Never leave lit candles unattended Ensure cigarettes are stubbed out and disposed of carefully Never smoke in bed Keep matches and lighters away from children Keep clothing away from heating appliances Take care in the kitchen! Accidents whilst cooking account for 59% of fires in the home Take special care when you are tired or when you ve been drinking. Half of all deaths in domestic fires happen between 10 pm and 8 am. West Sussex Fire and Rescue Service trust that you have enjoyed this course. If we can provide further courses or information please contact us on