The 456 thrived in an atmosphere made up of 25%
nitrosyl chloride, 22% hydrogen chloride,
20% nitrogen, 12% fluorine, 9% hydrogen cyanide,
6% acetone, and 6% phosgene.
The word atmosphere is a stretch but it is the gas/fluid content of their heads.
added this to my comment section:
Cleanup: A bunch of nasty toxins are let free after killing and that includes Fluoride, best to mop up with Boron and NAC