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I thought exposed non-skinned styro in a living space was a no-no, due to
the outgassing if it gets exposed to flame?


When used as wall insulation, code requires it to be covered with
sheetrock.. Fact is, the material is less of a problem than most other
items in the room. First, the material must be the modified version of
polystyrene (all foam sold for insulation is). That means it has self
extinguishing properties. It will not burn unless there is another source
of ignition.

Factory Mutual did some testing in their labs some years back. They set up
a "typical living room" with different wall coverings. One test was with
the vinyl covered paneling that was popular some years ago. Another test
was exposed foam insulation. A wastebasket with papers was set in the
corner and lit on fire. The paneling made horrific flames and smoke while
the foam plastic burned up a couple of feet above the wastebasket and went
out on its own.

The main product of combustion of burning styrene is soot. Of course, it
makes a fair amount of soot and you don't want to breath it, but it does not
produce deadly gasses. It is essentially the same as burning oil, the raw
material it is made from.

If the insulation on the windows is burning, you have much more serious
problems that the products of combustion from the insulation will cause.