A slight correction to Art Reblitz's excellent summary.  Methyl bromide
does not kill by asphyxiation, it is instead a very active alkylating
agent (like mustard gas), adding methyl groups to sulfhydryls in a wide
range of enzymes and other proteins, thus rendering them non-functional.

Exclusion of oxygen (readily done with such non-toxic alternatives as
nitrogen or carbon dioxide) is not effective on woodworm, at least on
a scale of days.  In humans the primary effect of methyl bromide is
neurotoxicity, resulting in rapid death.  It is a very difficult
toxicity to reverse, so there are not very effective antidotes.  This
definitely falls into the "don't try this at home" category!

When I was trying to figure out what to do for my infested Violano
I spoke to conservators at the Boston Museum of Fine Arts and the
Society for the Preservation of New England Antiquities.  They
recommended fumigation as the most effective treatment, with prolonged
(months) freezing at zero F as a less-effective alternative.  They
strongly recommended against any applied pesticide because (1) they
don't work and (2) residual toxicity.

There's a facility near Boston that fumigates whole semi-trucks at
a time, apparently mostly to get rid of critters in shipments of pasta
(don't think about this too long!).

Cheers,
Roger Wiegand
Wayland, Massachusetts, USA