Thanks Ryan. 

George, I have a couple of air quality meters in my shop to help me know when the airborne dust levels are still high.  The ones that are really-really (2 reallys!)  bad for you are not visible so light is not going to tell you when they still hanging around.  They also take longer to settle out of the air than the ones you can see.  It can take a couple of hours or more. especially if you have a fan or any sort of heating or cooling running.  You can see the meters I use in my Corsi-Rosenthal Filter box write up.  It has been a little over a year and the filter does a great job of clearing the air -- usually within about 15 minutes which allows me to take my dust mask off more quickly.  There is noticeably less fine dust settled around the shop too.  The air filter comes on automatically when it detects motion in the shop so it is pretty much always on while I am out there.  Note that the meters also give VOC and formaldehyde levels.  

--Nathan, TX. Hire the lazy man. He may not do as much work but that's because he will find a better way.