Hair dryer is overkill, especially for an insulated ferm chamber.
In a past life I managed a company that sold and repaired hot tubs. My techs used hair dryers when a tub broke down to keep the pipes from freezing. I have seen one maintain 83+ degrees with below zero ambient temps for days on end.
I use this one
the teflon is very nice. I've been using this style in my garage for years even if the bulb does break it doesn't drop shards.