I drive lots of dusty gravel roads here in my home state of Oregon in my NV200 2013 that I had converted to a camper van a couple of years ago. I too have been very frustrated by the amount of dust leaking into my camping gear especially in the rear storage area under the bed. So on a trip to southeastern Oregon this past week I tried a trick I'd read about on a car forum some time ago. What I did was drive with my windows closed, the air set to recirculate and the cabin fan set to low. I even ran the air conditioner at times when I felt too warm. This is supposed to create positive pressure inside the van and keep dust from filtering in and amazingly it worked. After driving seventy plus miles over gravel roads around the Hart Mountain area I found very little dust in my gear compared to other times I've driven on gravel roads for extended periods.