atmos: fix everlasting fires

Fires were checking against a non-reduced air sample for existance, so
the reduced sample wasn't working in zburn when it failed the check.
Also fixed volatilefuel not being scaled in the phoron reagent.

Signed-off-by: Mloc-Argent <colmohici@gmail.com>
Merge pull request #5328 from Mloc/bs12-firefix

atmos: fix everlasting fires