of brown recluse or hobo spiders (both of which have necrotizing venom)
given almost zero information.

Hire an exterminator.

I saw a show on Discovery or TLC about necrotizing venom. Yikes!!!
You'd be better off getting napalm on you then this stuff. DAGS these
type of spiders for a pic and be sure that you don't have anythink like
that in your shop.