Shop Vac with HEPA filter--does it work?

Has anyone used a HEPA filter on a Shop Vac? I'm looking at the Shop-Vac 90340 CleanStream Replacement Cartridge Filter to use in cleaning up a storage room in my shop. It may or may not have some nasty dust and other stuff that I would rather not breath or put in the air while cleaning. My theory is it will do little good to vacuum the place if the vac exhausts the dust to settle on other surfaces. My thought was to use this filter with a foam filter (pre-filter) around it to catch the big stuff so that it would drop off the filter when the vac is turned off. I need to keep it highly portable so I don't want go the 5 gal. bucket/separator lid route. Any opinions or suggestions?

I use my Shop Vac in conjunction with my ROS. The HEPA filter I have installed on it works very well at keeping the fine particules inside the vac. To further help reduce the fine particulates, I also use the drywall dust bags. Between the HEPA filter and the drywall bags I'd guesstimate I'm capturing over 95% of the sawdust. Before I started to use the drywall bags I was having to clean the HEPA filter far too often for my liking. The bags have really made a big difference and now I can go much longer between cleanings.