Usually sanding hotcoat…100 grit dust?
How about 220 grit? 400 grit?
20 microns or are they less?
A “speck” of dust that is visible to the eye would be around 200 to 500 microns. You would need a microscope to see a 20 micron particle.
1/2 the width of a human hair is 35 microns
Liki,
Here’s some info to help you get an idea of particle size. Keep in mind that 1 micron is 1/1000th of a millimeter. I’d guess you have a small portion up around the 500 micron size, as Surfersensei suggests, and quite a bit more in the sub 200 range. 20 microns is small but when accumulated it can be very easy to see. For example, the cement my company makes has a particle size profile where 100 percent of the particles are less than 80 microns and 40% is below 5 microns.
To find out the size of your sanding dust you’d need a particle size analyzer. Not exactly something you find in every garage. Certainly it’s safe to say 100 grit will make finer dust than 400 grit, and both will make a wide range of particle sizes.
I don’t know why you’re asking, but if it has to do with lung protection, most dust masks filter out 95% of 0.3 microns. The bigger problem is getting to fit your face properly. That’s where a proper respirator with good sealing rubber face piece comes in.
The “Jet” model 1200 collects dust down to 2 microns in size.
I sanded a tiny bit without a mask or respirator, it made my mouth feel funny (I was really hot, it was 113 out at the time, breathed through my mouth on accident). I wore one from my school’s auto shop and sanded a ton, no wierd feeling. I figure if it get’s the paint mist out, it must get dry dust out.