system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] What is the point of giving First Order troopers helmets that can filter smoke, but not toxins?
gpt
I'd imagine it's because FO do not expect to encounter weaponized toxins. Only one glimpse in Earth history  shows how awful an idea chemical warfare is. But yeah, they naturally assume they'll encounter smoke, all the smoke from plasma or laser hitting its target and possibly igniting small forest fires etc. Not to mention all the burning they do otherwise.

Also, I'd second the notion that helmets with less filtration are cheaper and less bulky. It's economically sound, and the helmets they have already encumber them enough in combat. Plus, as the helmets are meant to look menacing (and dehumanize the troops, if you want to go meta), this added filtration probably could mess with that too.