Hepa filter is the finest available in controlling dust meaning it traps .5 or finer dust particles which is smaller than diameter of a human hair.... I have this on my shop vac which just replaces the filter the shop vac comes with, I also have a Dust Deputy (Oneida) on shop vac this captures almost all dust before it even goes to shop vac,the small hose that shop vac sells will fit into the back of Dewalt sanders when using this hookup I do not see hardly any dust when sanding ,,,, I am trying to keep my lungs clean A lesson learned the hard way last year while building some swings sanded some Cypress for 2 days almost I coughed for over a week and had headaches so this year I did not work on anything till I got my dust collection issues straight......
Just to clear up some possible confusion;
A human hair is between 40 and 120 Microns.
A standard dust collector filter is rated at around 5 microns.
A HEPA rated filter in the U.S. must be capable of removing 99.97% of particles .3 microns and larger. (1/3rd of a micron)
So there is a BIG difference between a standard filter and a HEPA filter. Recent studies have determined that these Ultra Fine particles cause much of the damage to our lungs.
This is why many manufacturers are beginning to offer HEPA rated filters for their equipment.
Another issue is the fact that after a standard filter filters out what it can, it lets the rest of the fine dust back into the shop where it's very tiny size allows it to float in the air for extended times.
This is what the Air Cleaner type of filter is used for. The job of the Air Cleaner is to filter the air in your shop for fine airborne dust. They typically have a finer standard filter than a Dust Collector though not all come with a HEPA rated filter. They also typically are left on for a significant time after making dust to scrub the air clean.
To clear the air in my garage shop I just open all the doors and place a commercial type high CFM fan in one of the back doors while making dust and for a time after sweeping and vacuuming.