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for landing.
Since the engine had stopped, no one
heard the aircraft glide to a landing on the
open field. “I was alone, disoriented, injured,
and had a severe headache and ringing in
my ears,” he said.
The aftermath of a near-fatal accident
caused by carbon monoxide poisoning.
Extracting himself from the aircraft, he
struggled a quarter of a mile through snowcovered
fields for help, finally stumbling
onto a farmhouse. Dr. Frayser was taken
by ambulance to a hospital, where the
emergency room physician put him on 100
percent oxygen to overcome near-fatal blood
levels of carboxyhemoglobin.
Carbon monoxide poisoning from a
cracked muffler had allowed the deadly,
odorless gas to seep into the cabin through
the heater and caused him to fall asleep. The
crack, which had apparently opened after
the last annual inspection, was concealed
by the heat shield and could not be detected
during the pre-flight inspection. “The crack
could have been there for a long time, just
waiting for someone to turn on the heater,”
he said. Frayser did not have a carbon
monoxide detector on board to alert him of
its presence.
Another 30 minutes in the air might have
been fatal. Carbon monoxide poisoning
would have claimed another victim.
Overlooked Safety Issue
Carbon monoxide poisoning is a safety
issue that pilots tend to ignore, even though
it is the most common industrial poisoning
accident in the United States. When carbon
monoxide poisoning occurs, it can have
significant and fatal consequences for
aircraft occupants.
Carbon monoxide is a by-product of the
incomplete combustion of carbon-containing
materials. Aviation fuel contains carbon and
is a ready source of carbon monoxide when
burned. Expect carbon monoxide whenever
an internal combustion engine is operating,
and even though piston engines produce the
highest concentrations of carbon monoxide,
exhaust from turbine engines could also
cause carbon monoxide poisoning. In
addition, expect carbon monoxide whenever
a fire occurs, as commonly happens in a
post-crash environment.
Carbon monoxide is truly a hidden
menace because by itself, it is both a
colorless and odorless gas. An individual
would not be aware of its presence until
symptoms developed, or during treatment
it was determined exposure had occurred.
The least desirable situation would be
incapacitation. In this case, the victim
is powerless to do anything about the
2
exposure. Fortunately, because it is a byproduct
of combustion, carbon monoxide is
frequently associated with other gases that
do have an odor and color.
By avoiding an environment with known
combustion fumes, you will also avoid
carbon monoxide. The true problem comes
when exposure is so gradual that you don’t
perceive it. You can become incapacitated
before you can vacate the environment. In
an airplane, the result most likely will be a
fatal accident.
Why Carbon Monoxide Poisoning
Should Concern Pilots
What is not known is the full extent of
carbon monoxide poisoning in aviation.
Analysis of toxicology samples from fatal
U.S. aircraft accidents between 1967 and
1993 showed that at least 360 victims
had been exposed to sufficient carbon
monoxide before or after the crash to impair
their abilities. Non-fatal carbon monoxide
poisoning in aviation is likely a more
common occurrence than currently believed.
No one is sure how many times pilots or
passengers became ill, not realizing they had
been exposed to carbon monoxide. Because
no significant incident or incapacitation
occurred, the matter was not reported and,
hence, not investigated. Symptoms that
could be attributed to airsickness, altitude
hypoxia, fatigue, or a variety of other
conditions actually could have been carbon
monoxide poisoning.
Exposure and symptoms may occur
repeatedly over several flights until, finally,
someone suspects carbon monoxide or,
tragically, an accident claims a victim. No
database presently exists that accurately
collects or tracks non-fatal aviation carbon
monoxide exposure information.
Toxicity Mechanism
Carbon monoxide has a very high affinity
for hemoglobin, the molecule in blood
responsible for transporting oxygen through
the body. Carbon monoxide has affinity of
240 times that of oxygen. Carbon monoxide
tightly attaches to the hemoglobin, creating
the compound carboxyhemoglobin, which
prevents oxygen from binding, thereby
　
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