Security without atoms

During the daily commute, people are now used to the empty signs proclaiming no tools left in this vehicle emblazoned on the rear of trade vehicles, presumably in a feeble attempt to ward off theft.

But I followed one such van home the other night that had a curious version of the standard sign on the back:

Brilliant! I had visions of the owner attaching a giant pump to the top and sucking all the air out, perhaps to make it impossible to open the door due to the vacuum inside. Fabulous security measure: only by re-pressurising the car in the morning (or smashing the window) would anyone be able to open the door and steal the contents.

Or maybe by filtering out the oxygen, leaving just the atmospheric nitrogen behind, they could create some sort of inert chamber to limit corrosion of whatever else was in the van.

Shame it was a medical supplies van and they probably meant oxygen canisters. Way to spoil the fun.