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You are not required to put the fire out – but if you attempt to extinguish a fire then you need to know your fire extinguishers. Only attempt to put a fire out if you have a clear exit from the room. Do not turn your back on a fire and keep your exit from the room open and accessible at all times. Extinguishers will work for approximately 30 seconds – if you have not put the fire out in that time – leave the area immediately. Once you leave a burning room, do not re-enter. Close the door to a room with a fire. Leave the door unlocked as the fire department will need to enter. If you know the type of fire and contents of the room, please advise the Chief Fire Warden for the building or the Fire Department personnel.
Types of Fires:
There are three types of fires listed on the above diagram; not all extinguishers can be used on each type of fires.
Type A fires are the ordinary combustible materials such as wood, paper, cloth, etc…
Type B fires are flammable liquid fires such as gasoline, paints and solvents, alcohols, acetone, etc..
Type C fires are electrical fires.
There is a fourth type of fire not listed on the above diagram – Type D fires are flammable solids. When labs have flammable solids, a special type of fire extinguisher is required. You must contact Fire Safety at Facilities & Operations to advise that your lab has flammable solid so they can provide you with the appropriate extinguisher.
The type of fire will determine the type of extinguisher that can be used. In many university labs, Fire Safety have supplied the multipurpose dry chemical extinguishers because they cover all three types of fires.
Water extinguishers are good for Type A Fires only. Type A fires are wood, paper or cloth fires. You cannot use a water extinguisher for a Type B fire,(flammable liquids), as flammable liquids are lighter than water and will float on the surface of the water. This will simply aid in the spread of the fire. You cannot use a water extinguisher on a Type C fire, (electrical fire), because you run the risk of receiving an electrical shock. Water is an electrical conductor so as the water spreads out, the chance of electrocution increases.
There are special water mist extinguishers that work well on a Type A & C fires. Such extinguishers are ideal for Class A fires where a potential Class C hazard exists. The misting nozzle provides safety from electric shock and reduces the scattering of burning materials. This type of extinguisher is not found in labs because the U of A stocks labs with a multipurpose dry chemical extinguisher, a type of extinguisher that works best for mixed fires.
A CO2 extinguisher is not a good choice for a Type A fire, (wood, paper, cloth), because of the force of the CO2 gas being expelled from the extinguisher. When this type of extinguisher is used on a wood, paper or cloth fire, the burning items are blown around the room by the force of the CO2 gas, thereby aiding the spread of the fire. Secondly, a Type A fire will usually re-ignite as soon as the CO2 gas dissipates.
The CO2 extinguisher works well on a flammable liquids or an electrical fire – Types B or C fires. They work well on an electrical fire in that they do not leave a messy residue on delicate electrical equipment such as a dry chemical extinguishers would. The CO2 displaces the oxygen at the surface of the fire, effectively smothering the fire. However, the fire can re ignite once the CO2 gas dissipates if the ignition source has not been removed.
A CO2 extinguisher has a wide nozzle that locks into place. Do not hold onto the nozzle when firing the extinguisher, this nozzle will get very cold as the CO2 gas is expelled; CO2 gas has a temperature of minus 66C. If you are holding onto the nozzle you will receive a cold burn.
Dry Chemical Extinguishers:
The multipurpose Dry Chemical Extinguisher for a Type A,B,C fire is what you will find in most university laboratories that contain chemicals. These extinguishers have the most range of compatibility with items found in a lab and are good for most types of fires. A Type BC fire extinguishers contain sodium or potassium bicarbonate and a Type ABC fire extinguishers contain ammonium phosphate. They have an advantage over CO2 extinguishers in that they leave a blanket of non-flammable material on the extinguished material which reduces the likelihood of re ignition. However, they make quite a mess and the fine powder will irritate the throat and lungs.
The contents of these cylinders can pack down over time and when a person goes to use them they may not fire. If this happens, turn the cylinder over and rap it sharply on the top to loosen the compacted powder inside. Then try firing the cylinder again. If the cylinder will not fire – leave the area immediately.
All fire extinguishers have fire ratings stamped on them. You should familiarize yourself with this rating. For example, a dry chemical cylinder may have 2A, 10 BC stamped on it; this means that the contents of the cylinder are enough to fight 2 square meters of a Type A fire or 10 square meters of a Type B or C fire. Higher numbers mean more firefighting power.
Type D Fires; Flammable Solids:
Flammable Solids – requires a Class D Extinguisher
There is a fourth type of fire not listed on the above diagram. Type D fires are flammable metal fires such as magnesium, potassium, sodium titanium, as well as alkyllithiums, Grignards and diethylzinc. Type D fires burn at high temperatures and the metals will react violently with water, air, and/or other chemicals. This type of fire requires special metal/sand extinguishers. They work by simply smothering the fire with powdered copper metal or sodium chloride (NaCl). You should have an approved class D extinguisher if you have flammable metals in your lab area. The type of class D extinguisher depends upon the type of flammable metals you have; you will require the copper extinguishing medium for lithium and lithium alloy metals; the sodium chloride extinguisher works better for fires involving magnesium, sodium, potassium, uranium and powdered aluminum.
Always advise Fire Safety at Facilities & Operations if you have used any University fire extinguisher or if the seal has been removed.
Fire Extinguisher Training:
Yearly fire extinguisher courses are available through the Facilities & Operations, Fire Safety Division during the months of May, June, July, August & September. The dates and information regarding the fire extinguisher courses are posted on their web site, Sign up for their course if you would like to learn how to operate a fire extinguisher effectively. Such training can be invaluable to you at home or at work in the event of a fire emergency. You should never attempt to put a fire out until you have been trained in the proper use of a fire extinguisher.