A New Gas - Helium

[Marquesas]

It would be kind of neat if there was a way to add chemicals to the gas process, with a variety of side effects, such as turning the pipes into a neurotoxin delivery system, or causing the pressure in the engine to go waaay up because you added some vodka and some liquid oxygen or something.

As cool as this sounds, the reagent and the gas system are two very distinct systems, not to mention introducing 100+ new gases would place a lot of load on the already bulky atmos.