CAUSES AND PREVENTION OF MOTOR FIRES.
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By the Chief Officer of a Fire Brigade.
AS wasobserved in a recent issue of The Commercial Motor, many fires are caused by the presence of naked lights in the vicinity of motor vehicles when their fuel tanks are being replenished with petrol. Generally petrol is treated very lightly by the public. Its properties are actually little known, and it is only its high ignition point that preserves the users from feeling it powers more frequently as a destructive agent.
If it were passible to get a return of all fires in which the ignition of petrol was definitely shown to have been the cause' the figures would surprise -the uninitiated. These fires happen on the road, in the garage, industrially and in the home.
A gallon of petrol will produce, in conjunction with air, 5,430 gallons of high-explosive gas. The gas is about 21 times heavier than air ; it will sink and float along the ground and may get to a point distant from its source and it will flash back if a naked light is in its path. An authentic case once happened at Exeter, where the distance was proved to be 53 feet.
Tobacco smoking in any form near a motor when its tank is being replenished with petrol should be discouraged in every possible way. When the tank is being charged, displacement of gas must take place, whilst the pressure is subject to the speed at which the petrol is flowing into the tank. This pressure with the current of air prevailing can carry the vapour some distance before it becomes diffused.
Petrol cannot be blamed for all the fires. In practical experience it has been found that (1) overheating of brakes (2) overheating of exhaust, (3) arcing at terminals on accumulators (in celluloid eases), (4) defect in switchboard, (5) hot pipe in B28 driver's pocket, (6) sparks from locomotives, both on rail and road, all add their quota to this event. Then there are troubles due to defective carburetters, and to road shocks, involving breaking of petrol pipes, the leaking petrol being ignited from sparks from wheel and road contact or defective wiring or backfire due to faulty valves.
Comments in The Commercial Motor upon the underside of motor vehicles being saturated in oil
are timely. Often motor fires would present little difficulty and could be extinguished without much material damage if there were not this saturation
of oil, and, generally, these fires happen on the motors where maintenance both from a mechanical and cleanliness point of view is below the standard.
Every licensed passenger vehicle should carry a carbon tetrachloride extinguisher of at least 2 quarts capacity, and the large vehicles of over 25 seating ca.patity should have a 2-gallon foam extinguisher in addition.
The latter provision is most important where vehicles are traversing areas outside towns, or even working in the smaller towns where permanent motor fire brigades are not available to answer a call in a few minutes.
Owners of private and commercial vehicles would be wise to consider and to provide their drivers with first-aid fire extinguishers of the nature of those mentioned.
Foam extinguishers, in some cases emitting what is called fire snow, produce a yeast-like substance which floats upon petrol and oil and also adheres for a time to substances and smothers the fire. The bubbles in the foam are filled with CO e gas and this adds to the efficiency of the foam or snow.