If you're around smokers after FUE but don’t smoke, does this harm you? I stopped smoking since FUE

There is no evidence that inhaling passive tobacco smoke will have an effect on graft survival. Active nicotine exposure could have a vasoconstriction effect, so avoiding active smoking is a smart thing to do for the first few weeks after your transplant.

Being around people that smoke will not harm your hair follicles.  If you are concerned it is best to stay away from smokers.

Unless you are trapped in a closed room whilst a person smokes one cigarette after another it is highly unlikely that you will be affected, in terms of a hair transplant, by second hand smoke.