Ask A Scientist Chemistry Archive

name         C. S.
status       educator
age          40s

Question -   What is the chemical composition of smoke, and what
compounds (and why do they) cause smoke odor to linger indefinitely after
a fire?  To what extent are these compounds related to those responsible
for skunk odor?
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C.S.

Assuming you are asking about smoke from burning organic material and
disregarding the combustion products, carbon dioxide and water, smoke is a
complex mixture of aerosols and vapors composed of particles of carbon, and
a bewildering variety of organic compounds whose exact identity is dependent
upon the nature (composition) of the fuel burned, the amount of oxygen
present, and the temperature of the fire.

Many of the organic vapors have relatively high boiling points that, when
condensed on surfaces, can be very difficult to remove. Some can actually
soak into the surfaces they contaminate. Often these compounds are not water
soluble. Therefore washing with water isn't effective in removing them.

If the fuel contained the element sulfur, some of the combustion products
may have a skunk-like odor that is tenacious in its ability to cling to
surfaces and persistent in odor.

Sometimes smoke damaged materials can be at least partially deodorized by
exposing them to the oxidative effects of ozone in the hope that oxidation
of the odorous materials may render them less odious, or amenable to the
cleansing effect of detergent washing.

Regards,
ProfHoff 527
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First, skunk odor is caused primarily by butyl mercaptan (CH3CH2CH2CH2-SH)
and is not related to the odor of smoke. The composition of smoke depends
upon what the fuels are, how much oxygen is available, the flame temperature
and  so on. But there are some generalizations that can be made. There are
respirable particles of carbon (soot), cellulose (from unburned, or
partially burned wood), asbestos (if there was insulation present), metal
oxides. There are gases-- CO2, CO, SO2, HCl, various nitrogen oxides, and
volatile organic compounds of many types. Free radicals are also present.
The components of tobacco smoke have been thoroughly studied. Search
www.google.com for terms like "wood smoke components", "tobacco smoke
components" and so on. There is a lot of info on the web.

Vince Calder
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