Dust problem with Ford Transit

I have fibreglass canopy on dual cab ute which always let dust in. I fiited 2 ventilators from a marine store. No problem since. Cost unde $25.
Link to https://www.whitworths.com.au/main_itemdetail.asp?cat=156&item=92551&intAbsolutePage=1

Tawsey.
The problem you have is that van acts like a big set of bellows, sucking dust in every small opening. The solution is to provide a positive pressure inside the vehicle. the best way to do this cut a hole in the roof above the windscreen and fit an air scoop facing forward. the scoop needs to be about 25mm high and about 500mm wide. place some mesh inside the scoop to keep out insects. Eric.

Transit is not designed or intended for dusty environments. Always drive with the passenger compartment vents OPEN (NOT recirc) and the door glass up but the volume of the van may require more airflow. You may find a few non-sealed equipment (from the Apollo fitout) holes etc underneath, too

There is a low pressure area developed at the rear of any vehicle - especially one with a bluff end like yours. Dust is sucked up from the road and will be sucked inside. The only way to prevent this is to pressurise the vehicle so that the inside is at a greater pressure than the outside. Air will then blow out from the vehilce rather than into it. Pressurisation is done by having the air controls set to fresh air (not recirculating) and use the fan. You must also keep the windows closed. If you are in dusty conditions, using the air con will help to settle the incoming dust by condensing it on the evaporator fins.

You should always run the vehicle with the air flow on Fresh rather than recirc, simply because if there is an exhaust leak, there is less chance of getting CO (Carbon Monoxide) into the cabin. Most manufacturers recommend using recirc, but I suspect that is because they have skimped on the Aircon size and would be getting heaps of warranty claims forinefficient aircon. For all but extreme outside temperatures, fresh air is fine for the A/c.

Clark Rubber is your friend :) They sell strips of foam that is adhesive on one side. I've ran this around all my doors on the GQ and it works great.

My car is so dust proof now that it's actually air tight. I need the window down a little bit to close the door without excessive force :) I can be away for weeks and the interior is spotless.

Thanks everyone, seems like the foam and using outdoor air may be the best bet. I will be trying very shortly anything is better than coming home to a major cleaning job.
Tawsey