Id say 8 second fire immunity as long as you extinguish a fire so it doesnt become chemspray v2, obviously this is meant to synergise with pipe wrench and a biit with mallet so this may change the buff meta since its possible to either: keep a few, or a single component alive for a long time but you need to be tied to them which can open up interesting strategies (ie,flame junker main engine and shred hull with gat)
Might even go well with gunner if it gets 2 tool slots since you can indefinitely maintain your gun which is darn useful on heavies