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SMOKE TOXICITY

Th e specter of fi re in the air is a pilot’s recurrent 

nightmare...

F

IRE is an integral part of our everyday life, 

and smoke is one of its products. There 

have always been efforts to control fi re 

and use it for constructive purposes, but even 

then, accidental fi res do occur and fi re continues to cause loss of lives and property.

Uncontrolled fi res threaten homes, factories, and transportation systems. The specter 

of fi re in the air is a pilot’s recurrent nightmare, carried over from the early days of fabric covered aircraft, when the time between 

ignition and loss of the aircraft could be measured in relatively few minutes.

Modern aircraft benefi t from fl ame retardant 

materials and improved fi re extinguishing systems to such an extent that in-fl ight fi res are 

rare occurrences.

However, survivable crashes followed by 

fi re happen, primarily from fuel spills around 

the downed aircraft. In the confi ned environment of an aircraft cabin, the presence of 

smoke automatically indicates the existence of 

an emergency situation.

Extinguishment of fi res obviously has fi rst 

priority, but smoke inhalation should be 

recognized as a very real danger while this is 

being accomplished. Inhalation of toxic gases 

in smoke is the primary cause of fatalities in 

most fi res—this is true whether the fi re is in 

an aircraft cabin, a residential bedroom, or a 

high-rise building. Smoke gases do not need 

to reach lethal levels to seriously impair pilot 

performance. Sublethal exposures can cause 

even experienced pilots to make potentially 

fatal mistakes. 
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In view of the seriousness of any aircraft 

fi re, let us examine the various aspects of fi re 

and smoke.

FIRE

Each fi re is diff erent...

F

ire is a complex, dynamic, physicochemical event and is the result of a rapid 

chemical reaction generating smoke, heat, 

fl ame, and light. Each fi re is different. Smoke 

composition and heat generated in a fi re depend on types of burning materials and environmental conditions.

SMOKE

Its gases could be toxic...

S

moke is a complex of particulate matter, 

as well as a variety of invisible combustion gases and vapors suspended in the 

fi re atmosphere. Smoke may diminish light and 

obscure vision, and its gases could be toxic.

SMOKE GASES

Carbon dioxide levels increase and oxygen 

concentrations decrease...

Carbon monoxide and hydrogen cyanide 

are the two principal toxic combustion 

gases. Most cabin furnishings contain 

carbon and will generate both carbon monoxide and carbon dioxide when burned; carbon 

monoxide can also be released from faulty 

cabin heaters. Burning wool, silk, and many 

nitrogen- containing synthetics will produce the 

more toxic hydrogen cyanide gas. Irritant gases, 

such as hydrogen chloride and acrolein, are 

generated from burning wiring insulation and 

some other cabin materials. Generally, carbon 

dioxide levels increase and oxygen concentrations decrease during fi res.

SMOKE EFFECTS

At high altitude, the effects are greatly 

enhanced...

Visual smoke can delay escape from a 

fi re, while the irritant gases can induce 

tears, pain, and disorientation. The visual obscuration is obvious, but the subtle effects 

of carbon monoxide and hydrogen cyanide 

inhalation, although less readily detected, can 

cause physical incapacitation and subsequent 

death. Toxicologically, carbon monoxide combines with the hemoglobin in blood and interferes with the oxygen supply to tissues, while 

hydrogen cyanide inhibits oxygen utilization at 

the cellular level. Carbon dioxide, a relatively 

innocuous fi re gas, increases the respiration 

rate causing an increase in the uptake of the 

other combustion gases. The decreased oxygen 

level found in most fi re scenarios further enhances the problem of getting enough oxygen 

to the biological sites to maintain normal function. Continued inhalation of these gases can 

result in severe hypoxia. At high altitude where 

oxygen levels are lower, the effects of carbon 

monoxide and hydrogen cyanide are greatly 

enhanced.
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SIGNS AND SYMPTOMS 

Not all sy mptoms w ill necessarily be 

experienced... 

Carbon monoxide poisoning produces 

headache, weakness, nausea, dizziness, confusion, dimness of vision, 

disturbance of judgment, and unconsciousness 

followed by coma and death. Although carbon 

monoxide causes deleterious effects on the 

central nervous system, death usually occurs 

from cardiotoxicity. 

Not all symptoms will necessarily be experienced by every individual exposed to this 

gas. Some have succumbed from inhaling low 

carbon monoxide levels, while others have 

survived breathing higher concentrations. 

Hydrogen cyanide poisoning signs and symptoms are weakness, dizziness, headache, nausea, vomiting, coma, convulsions, and death. 

Death results from respiratory arrest. Hydrogen cyanide gas acts very rapidly—symptoms 

and death can both occur quickly. 

SURVIVAL 

Knowledge of the less obvious hazards and a few 

simple preparations can increase one’s chances... 

There is no universal best procedure to follow in the event of an aircraft fi re because 

no two fi res are likely to be the same. Extinguishing the fi re, if possible, is the immediate 

priority. An equally obvious second priority is 

to breathe as little smoke for as short a duration 

as possible. 

Some larger aircraft are supplied with portable, self-contained breathing masks for the 

crew, but small private aircraft usually are not. 

Any cloth held over the nose and mouth will 

provide protection from smoke particulates; if 

the cloth is wet, it will also absorb most of the 

water-soluble gases (i.e., hydrogen cyanide 

and hydrogen chloride).

Cabin venting will reduce the concentrations of combustion gases, but is not usually a 

viable option while actually fi ghting the fi re. 

Knowledge of the less obvious hazards and 

a few simple preparations can increase one’s 

chances for survival in an aircraft fi re. A small, 

hand-held fi re extinguisher can be used to put 

out small onboard fi res. Careful inspection 

and maintenance of cabin heaters will minimize the chance of carbon monoxide leakage 

into the cabin air system. A carbon monoxide 

detector could also be installed in the cockpit to detect the presence of this colorless, 

odorless gas. As always, planning your probable actions before an emergency arises will 

increase your chances for acting quickly and 

correctly. 

Remember... 

• Fires are the main hazard for the occupants of a survivable crash 

• A fi re generates smoke, heat, fl ame, and 

light • Inhalation of toxic gases in smoke 

is the primary cause of death in most 

fi res 

• Carbon monoxide and hydrogen cyanide 

are the main toxic gases in smoke 

• Exposure to carbon monoxide can also be 

the result of faulty heaters 

• A wet cloth held over the nose and 

mouth provides some protection from 

smoke inhalation 

• A small, hand-held fi re extinguisher 

should always be carried aboard general 

aviation aircraft 

• Install a carbon monoxide detector in the 

cockpit 

MEDICAL FACTS FOR PILOTS 

Publication AM–400–95/1 

Written by: 

Arvind K. Chaturvedi, Ph.D. 

Prepared by: 

FAA Civil Aerospace Medical Institute 

Aerospace Medical Education Division 

To order copies of this brochure, write:

Federal Aviation Administration 

Civil Aerospace Medical Institute 

Shipping Clerk, AAM-400 

P.O. Box 25082 

Oklahoma City, OK 73125