Here's a study:
When a match is struck, the first thing to burn is the head. The head of a
match contains a chemical cocktail that includes a lot of sulfur. In the
initial burst of combustion products there is therefore a lot of sulfur
dioxide. Sulfur dioxide is an extremely pungent substance, to which the
smell receptors are extremely sensitive. But it also has a very efficient
numbing effect on the sense of smell. You can smell a minute amount of
sulfur dioxide, but when you have done so, you will not smell anything else
for a while. Sulfur dioxide is a gaseous combustion product, so if this is
the main factor no-one wins the bet. It is not flame (plasma) nor smoke
(solid aerosol). You can easily test this one, because if it is the main
factor, other flames, like a spirit stove, a cigarette lighter, or a candle
will not mask smells nearly as effectively.
Taken from aother forum
The TV show "MythBusters" covered this topic and concluded
that matches mask the methyl mercaptan found in flatulence and feces. So, a match may not eliminate odors, but it will push them to the background. Most of the time, that's good enough.
So, I assume it is just covered up, not burned up, as shown in the Mythbusters experiment.