Go around and seal up all the vents but one or two.
Sealing them up means no access cracks or holes bigger than a dime size.
New vents, steel wool.. don't just use those spray foam aerosol can stuff, they will eat right through it...
Like others have posted on the bait , BUT DON'T use Decon unless you want to go look for the smell (dead ones)
There is secondary non kill rodent bait to use so even if the cat gets ahold of the rat after its eaten the bait it won't kill the cat..
The proper bait doesn't kill like the Decon does, it does the job be dehydrating the rodent so when it does die off it usually doesn't have the smell.
Trying to say this the best PC way I can think.... lol
Like others have posted get the bait boxes, like the ones Commercial business's use. You can see them along the outside on the ground along the walls of the places (Storage Units ,Walmart etc).. Or just inside the the vent hole that you left unsealed..
Glue boards work great IF you no have no problem dealing with a live rodent stuck on one not wanting to be disposed of..
No big deal with a 1 oz mouse but upwards of a pounder rat on one still alive and that's bring a shovel or ? with you to retrieve it..
They can be cannibalism I have seen the remains on both a snap trap and glue boards where yes they eat their own .... So check on the traps/bait boxes/glueboards often..
Not sure how big the place is or where its located? But you might want to make a little drawing of the place and number/count how many of snap traps, glue boards or bait boxes you have put out !!
Some people / neighbors might not like a box, trap, GB found on their property...
Anymore in this day and time better be safe then lawsuit sorry...
Good luck with your hunting...