EXHAUST GASES

Bay of Plenty Times, Volume LXXII, Issue 13333, 21 December 1943, Page 3

EXHAUST GASES

THE DANGER OF CARBON MONOXIDE POISONING Although the fatal results from breathing carbon monoxide gas a re to-da>' well known, fatalities still occur from this cause. The exhaust gases from an engine vary considerably, according t 0 the condition of the engine, the carburation and the lubrication. The exhaust gasses of petrol engines contain icarbon monoxide, which is a deadly poison, and for this reason the engine should never be run in a closed building. Many fatal accidents have occurred through neglect of this precaution. An analysis of a number of samples of exhaust gases shows some interesting comparisons. The following are the figures: The first sample was taken during a run in top gear at a speed of 28 m.p.h. with a light load. The exhaust contained 8.4 per cent, carbon dioxide (non-poisonous); 3.4 per cent, oxygen; 6.0 per cent carbon monoxide (deadly poison); 0.8 per cent marsh gas (asphyxiating); 2.7 per cent, hydrogen (non-poisonous); and 78.7 per cent, nitrogen (nonpoisonous). A sample taken during acceleration from rest to 18 m.p.h. showed less oxygen and less nitrogen, but 8.0 per cent, of the deadly carbon monoxide &as. / The same series of tests showed that the amount of carbon monoxide in the exhaust gases of heavy oil engines is extremely small, being less than 0.1 per cent, under most running conditions. In heavy traffic the amount of carbon monoxide emitted by waiting petrol-driven vehicles has aroused considerable controversy, and attempts have been made to measure the quantity in the air under normal conditions. But the amount of gas is very variable and difficult to estimate, and no definite conclusTons have been arrived at as to whether the amount is sufficient to be harmful to people in the streets. IE the engine and its accessories are functioning properly the exhaust gases should be clear and almost odourless. The two most usual defects are black smoke and blue smoke. The former indicates that the carburation is imperfect, and that an excess of fuel is being used; the latter denotes exsesslve lubrication, and therefore the transfer of oil from below to above the pistons. If the engine is mechanically sound, blue smoke is probably due to the level of the oil in the sump being too high. It is sometimes noticeable for a few minutes only when starting, and does not in that case need any attention. If the oil level of, the sump is within the proper limits and the exhaust is persistently blue, it is clear that too much oil is passing up above the pistons. This may be due to worn piston rings, broken rings, a scored cylinder, or to excessive wear of the cylinder walls, so that the cylinder is oval or of varying diameter. The leakage may be caused by a badly worn cylinder or piston, or by broken or gummed-up piston rings. A broken piston ring is, however. sometimes recognised by a peculiar scraping noise it makes. Should the trouble be caused by a gummed-up piston ring, the ring must be taken off and all carbon deposit carefully removed. If, as is more than probable, the ring has lost its elasticity, a new ring should be fitted. Where the trouble is caused by a broken ring the cylinder wall should he carefully examined to see if a groove has been scored by the corners of the broken ring. The groove can be welded up and the cylinder rebored, a process that can be undertaken by experienced welding specialists: or the cylinders may be lapped or ground and new pistons fitted. From the foregoing it will be seen that an excessive amount of blue smoke issuing from the exhaust may have serious consequences and should receive immediate attention, though it is only a dangerous symptom if it occurs from any other cause than excess of oil in the sump.