Urgent help about a spider?

ok...i have a spider underneath my computer desk....being as how its a small space down there....i could use anything such as a shoe to kill it....we didnt have any insecticides to kill it with...the only thing i could find that had a dangerous chemical in it was a can of dust off....so i sprayed the can upside down to release the chemical at the spider......i sprayed it weakly so it wouldnt blow the spider away....and then i just pressed it as hard as i could to get as much chemical on the spider as possible....do you think that the chemical in dustoff is potent enough to kill a spider??....its underneath my desk so it could bite my foot at anytime....so....plz help quickly cuz im not gonna sit at my desk til i know its dead