Garage gas fumes

[67carry-all]

Was very excited to recently find garage space for my truck. Was very unexcited to find out shortly afterwards that the garage now is full of gasoline fumes. Near as I can tell, likely coming from the tank through the vented cap. I was hoping to have the garage as an enclosed work space for the truck, but not really possible due to the fumes. Better with the garage door open, but not so great with the current cold and rainy weather. Anyone else with this issue, and more importantly, good ideas on how to solve it?