CARBON MONOXIDE

Dominion, Volume 31, Issue 41, 12 November 1937, Page 17

CARBON MONOXIDE

Eliminating Peril To Air

Pilots Carbon monoxide is the product of the imperfect combustion of carboniferous materials in internal-combus-tion engines, says James E. Edgerton in the “New York Times.” It is a colourless gas and, in average concentration, is also odourless. In larger concentrations, where it is extremely dangerous, it has a slight garlic-like odour.

Present in the exhaust gases of aviation engines in a ratio of from 2 to 7 per cent, of the total output, its greatest incidence occurs with large throttle openings and rich mixtures. Engine breathers may also be a source of contamination, particularly where there are worn rings and distorted cylinder

walls. There have been carbon-monox-ide readings of as high as 2 per cent, from this source. The inhaled air may be contaminated by carbon monoxide in several ways. In single-engine aircraft, which are particularly prone to this type of poisoning, there may bo seepage through the lire wall or through the fuselage openings. The engine exhaust may contaminate the slip stream and be directly fed into the cockpit. Turbulence may produce the same effect in the case of multiengined airplanes where the ventilation input is poorly located. Auother prevalent source of trouble is a poorly designed heating system which depends upon circulation of exhaust gases about heating members. Hot-water heaters eliminate this source of difficulty. Found by Air Corps. It is particularly significant that the United States Army Air Corps, in examining single-engine aircraft, found carbon monoxide in the amount of 0.026 per cent, where the power plant was a radial-cooled engine with short stacks and no collector rings. Their average on many runs was 0.0123 per cent., an amount dangerous to piloting efficiency. Carbon monoxide gas in itself is not harmful nor toxic. It is dangerous due to the fact that it produces oxygen starvation. Gradual starvation has been found to be more dangerous than sudden saturations by much larger quantities.

Carbon monoxide poisoning is a serious matter at sea level. The medical profession claims that thousands of persons arc daily affected to some degree by this gas. Serious, even fatal, poisoning is common. It is much more dangerous, however, in aviation. As higher altitudes are reached, the atmospheric pressure, as is well known, decreases in proportion. As Altitude Goes Up.

At. approximately 10,800 feet the pressure is two-thirds that of sea level. At about 17,400 feet the pressure is only one-half. The direct result is that the body experiences difficulty in obtaining an adequate supply of oxygen. If to this difficulty is added the oxygen deprivation caused by carbon monoxide poisoning, it is obvious that the situation is far more serious. Six parts of carbon monoxide iu 10,000 can produce coma in two hours. The Air Corps, on the basis of extensive research, has set 0.005 per cent of carbon monoxide as the maximum permissible amount in the inspired air. Of course, it, is desirable to eliminate every possible trace of this gas, but due to practical difficulties the bureau is inclined to believe that a permissible limit at sea level should not be higher than 0.01 per cent. The detection of carbon monoxide gas can be dividefl into two fields. First and most important of these, due to the fact that it is designed for preventive purposes, is the carbon monoxide indicator, which utilises the so-called

hopealite cell principle, this substance simply being a catalyst tor carbon monoxide. The second field of carbon monoxide detection depends upon sampling the blood of an individual suspected of having been subjected to carbon monoxide poisoning. This device is the so-called pyrotannic detector. This process can be used for living pilots who exhibit suspicious symptoms, or after death, with equal facility. The most significant symptom of mild carbon monoxide poisoning is a feeling of tightness across the forehead, usually accompanied by a slight headache. As the danger line is approached there is a decided loss of muscular power, vomiting, convulsions and coma. At this stage the pulse gradually weakens and the respiratory rate slows until there is a complete respiratory failure and death.