Bug spray

[Davy Jones]

I'm growing in a tool shed out back, I was pretty much sure I had everything covered, except for bugs. I have not seen any in the grow area yet, but I have noticed a couple spiders have started on a web right by the door. I plan on spreading some sevin dust around the yard this weekend, & I'm going to lay down some liquid stuff all around the perimiter of the shed...big time. I have a couple holes in the shed for intake & exhaust, should I turn the fans off while spraying? how harmfull could bug spray be to the plants?
The floor in the shed is plywood...it would be nice if I could soak that down in some bug spray as well, I know you shouldnt directly spray bug killer on plants, but what about spaying like around the pots, is that too close?

Anyway, thanks for any advice...