I live in the land of Daddy Long Legs and his various relatives
Once a year I place 3 Real Kill indoor foggers throughout my home set them off and go fishing for the day.
When I come home in the afternoon I open most of the windows
, turn the roof mounted swamp cooler on the roof.
Then the fun part even though the direction say open all the windows
and turn on the A/C and fans for 30 inutes.
I hook up my trailer and go back to my fishing spot and and come back home the following afternoon.
Been doing it for 7 years with no ill effects
If I had your spider problem I would open everything up inside the trailer, make sure there are no pilot lites lit and set of one bomb for a day and then let it air out.
You will get all the creepy crawleys that called your trailer home during the winter.