Pilots tend to think of
carbon monoxide gas as something produced by a defective muffler, a
faulty exhaust system, or a heater leak in the aircraft cabin. When they
perform their preflight check of the aircraft and find no breaks or
cracks, they feel reassured.
Yet, one of the more
common sources of carbon monoxide intoxication in an aircraft is tobacco
smoke. Carbon monoxide makes up about 3% of cigarette smoke and from 5%
to 8% of cigar smoke. A one-pack-a-day cigarette smoker is walking
around with about 4% to 8% of his blood saturated with carbon monoxide.
At ground level, he may be untroubled by this, but altitude flying
changes the picture.
Carbon monoxide has an
attraction for the red blood cells which is 200 times greater than that
of oxygen. If a molecule of carbon monoxide unites with a molecule of
haemoglobin, which ordinarily carries oxygen, they stick together like
glue. Oxygen doesn't stand a chance in the competition for haemoglobin.
Thus, the red blood cell cannot again carry oxygen into the system until
the carbon monoxide is expelled. For the pilot at altitude, whether he
is hypoxic because of low oxygen availability or whether he is poisoned
by carbon monoxide, the effect is the same.
Tobacco does more than
deprive the body of oxygen because of the carbon monoxide content in
smoke. It lowers the sensitivity of the eye and cuts night vision by
approximately 20%. Moreover, nicotine increases the body's heat
production 10% to 15% above normal creating added oxygen demands.
Ironically, the same cigarette that increases the demand for oxygen also
reduces the supply.
Careful tests have shown
that the carbon monoxide in tobacco smoke can lower the pilot's
tolerance to altitude by as much as 5,000 to 6,000 feet. In other words,
medically speaking, pilots who smoke are already "at altitude" before
they ever leave the ground. If you smoke, you will need to use your
oxygen systems earlier than a non-smoker would during ascent. If you
classify yourself as a moderate-to-heavy smoker, use your oxygen at all
altitudes during night flying. You will find day flying more comfortable
and safer - if you use oxygen above 5,000 feet.
In any given
concentration, carbon monoxide is just as lethal to the system whether
it is inhaled from exhaust fumes or from cigarette smoke. If you have
any doubt at all about your oxygen requirements as a smoker, take oxygen
with you to altitude - and use it.