I have trapped many a squirrel in a Have-a-Heart Trap. It is no fuss, no muss. Once you figure out how they are getting inside your whse -and close it up, you can trap them and release them outside.
I've trapped quite a few red squirrels and chipmunks in a Rat Zapper (Google it). Using sunflower seeds as bait, it works like a charm. And, they don't come back. I finally resorted to this method, as the little jerks always find a way to get in trouble around my place.