FAA Brochure - Smoke in the Cockpit

SMOKE TOXICITY

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

Fnightmare...

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 contin-

ues to cause loss of lives and property.

Uncontrolled fi res threaten homes, facto-

ries, and transportation systems. The specter of fi re in the air is a pilot’s recurrent night-

mare, carried over from the early days of fab-ric covered aircraft, when the time between ignition and loss of the aircraft could be mea-sured in relatively few minutes.

Modern aircraft benefi t from fl ame retardant

materials and improved fi re extinguishing sys-

tems 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 con fi ned environ-

ment 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.

In view of the seriousness of any aircraft

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

and smoke.

FIRE

Ea

Fch fi re is diff erent...

ire is a complex, dynamic, physico-

chemical 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 de-

pend on types of burning materials and envi-ronmental conditions.

SMOKE

I

Sts gases could be toxic...

moke is a complex of particulate matter, as well as a variety of invisible combus-tion 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

Cconcentrations decrease...

arbon monoxide and hydrogen cyanide

are the two principal toxic combustion gases. Most cabin furnishings contain

carbon and will generate both carbon monox-ide 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 concentra-tions decrease during

fi res.

SMOKE EFFECTS

At high altitude, the effects are greatly

e

Vnhanced...

isual smoke can delay escape from a

fi re, while the irritant gases can induce

tears, pain, and disorientation. The visu-

al 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 com-bines with the hemoglobin in blood and inter-feres 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 en-

hances the problem of getting enough oxygen to the biological sites to maintain normal func-tion. 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.

SIGNS AND SYMPTOMS

Not all symptoms will necessarily be

expe

Crienced...

arbon monoxide poisoning produces

headache, weakness, nausea, dizzi-

ness, 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 expe-

rienced 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 symp-toms are weakness, dizziness, headache, nau-sea, vomiting, coma, convulsions, and death. Death results from respiratory arrest. Hydro-gen cyanide gas acts very rapidly—symptoms and death can both occur quickly.

SURVIVAL

Knowledge of the less obvious hazards and a few

Tsimple preparations can increase one’s chances...

here is no universal best procedure to fol-low in the event of an aircraft fi re because

no two fi res are likely to be the same. Ex-

tinguishing 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 por-

table, 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 concentra-

tions 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 mini-mize the chance of carbon monoxide leakage into the cabin air system. A carbon monoxide detector could also be installed in the cock-pit to detect the presence of this colorless, odorless gas. As always, planning your prob-able actions before an emergency arises will increase your chances for acting quickly and correctly.

Remember...

• Fires are the main hazard for the occu-

pants 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

T o 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