Beware of Carbon Monoxide
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Whilst its Lethal Qualities are Fairly Widely Known, the Injurious Effects of a Small Quantity of this Gas
May Pass Unnoticed
THAT petrol-engine exhaust fumes contain a considerable proportion of carbon monoxide (CO) and that this gas is poisonous, is generally understood. Many of us, however, have been breathing these fumes for years and continue to enjoy good health, so the matter may not appear, at first sight, to be one for anxiety.
There has been a fair number of deaths, accidental and otherwise, from this cause, but generally these have occurred under conditions which are not met in a garage of any size. Although the gas can quickly cause collapse and death in a confined space with no ventilation, most workshops and public garages are sufficiently well ventilated to prevent the CO content of the atmosphere from reaching a dangerous value.
We are, therefore, less concerned with the aspect of fatality, than with that of possible injury to health and impairment of efficiency, but the following figures will throw some light on both questions. They give an idea of the magnitude of the quantities involved, of which few people have any knowledge.
The problem was examined by the gas companies, before the . motor industry had developed, CO being the dangerous constituent of coal gas. According to Mosso (" journal of Gas Lighting," 1902, 80, 1334), only 0.43 per cent. of CO in the air quickly proves fatal, whilst half this amount _ will have the same effect if breathed for any length of time.
A garage of length 20 m., breadth 10 m. and height 10 m. (approxi mately 62 ft. by 31 ft. by 31 ft.) contains 2,000 cubic m. of air-space; 0.43 per cent. of this is 8.6 cubic m. How B44 long would it take a 3-litre engine, running at 2,000r.p.m., to discharge this quantity of CO?
The quantity of gas expelled per cycle may be taken as equal to approximately the capacity of the cylinders, and the quantity of CO in the exhaust gas depends largely upon the efficiency of the engine ; with misfiring or faulty carburation, the percentage may be high. We will assume a value of 10 per cent, as a fair basis. [In a paper read recently by Mr. W. C. Whalley before the Institute of Fuel, a figure of 3.7 pr cent, was given.—End Thus 150 c.c. of CO will be discharged per revolution. This gives 150 multiplied by 2,000, or 300,000 c.c. per minute. It will, therefore, take 3.33 minutes to provide 1 cubic in. of CO. In order to discharge 8.6 cubic m. our engine must, therefore, run for about 27 minutes, Thus, in 27 minutes the air is charged with carbon monoxide to a degree sufficient to cause death in a few minutes. This assumes no ventilation whatever. To give the same result we might have three engines running for only nine minutes.
This demonstrates the need for good ventilation, even if the building be large. Although the exceptional conditions quoted, of having three engines running fast for nine minutes, with all doors, windows, etc., closed, are not likely to occur in practice, it must be obvious that if a 0.43 percentage of CO is lethal, a much smaller amount ' will be harmful.
Even if the atmosphere as a whole be safe, it is possible, for a man in a ventilation current carrying exhaust fumes, to breath an injurious quantity, sufficient to give a headache and to impair -efficiency. Some authorities quote a proportion as low as 1 in 10,000 as enough to upset anyone working at a skilled job, and to delay its satisfactory completion.
Recovery from partial toxwmia in the fresh air is rapid and complete, and as this generally fakes place more or less by accident as the worker moves about, it is often never realized that anything has been amiss.
From the fatality point of view, it is really necessary only that the worker should be fully aware of the properties of carbon monoxide, for him to take care to avoid dangerous situations. The onset of CO poisoning must seem mysterious to one not armed with this .knowledge, and he may make the possibly fatal mistake of sitting down in the polluted atmosphere to recover, instead of going into the fresh air.
From the health and efficiency point of view, only the employer can take action. Premises should be efficiently ventilated, and when engines are run for more than a few minutes, as, for example, when running them in after reboring or remetalling hearings, special provision should be made for leading the exhaust gases away.
Such a system need not be expensive to install. It may comprise ordinary Win. steam pipe, run along the wall, and ,having conveniently situated intakes provided with loosely fitting flexible hose. M.C.F.