All cabinets need a vacuum of some sort or the dust is too heavy to see what you are doing. A shop vac works well and yes you need an air inlet to replace dusty air with clean air. I simply start with a clean shop vac and then recycle the media that collects in the shop vac bin. I also have a course filter over the vacuum port in the cabinet that stops a lot of the media from entering the vacuum. But, if the filter is too fine is quickle becomes clogged and renders the vacuum ineffective. The vacuum filter collects and traps most of the corrossion which has been turned to dust by the blasting process. Sand should be avoided even with vacuum systems as a certain amount of the dust will escape into the surround air and it is not good to breath long term. Also, sand is good for only about two (maybe three) cycles before it loses its affectiveness.
