Hi,  This morning Richard Friedman touched on one aspect of using
compressed air that is a pet peeve of mine.  I see this all the time
on the home improvement TV shows.  I love Norm, but he does it too.

It's good that they use a dust mask when sanding or sawing or
blasting with compressed air.  And a proper respirator would be
better than just a mask if you are dealing with fine, powdery dust or
unknown powders like whatever is in a player piano that is decades old.
However, here is the part that bothers me.  After they finish the cut
or stop sanding, they take off the mask.  What a foolish thing to do.

After they produce all the dust, they take of the mask.  It's like the
dust magically disappears when they turn off the sander or the air hose.
Fine dust (the most dangerous kind) stays in the air the longest.  Chips
from a table saw are gone in a few seconds, coarse sanding particles
take a few minutes, but fine powder can take an hour or more.

So, what should you do?

1 - Collect as much of the dust as possible at the source, before it
gets airborne.  Use a real dust collector with a low micron filter,
not just a shop vacuum.

2 - Use a high volume air cleaner with a fine filter to clear out as
much of the remaining dust as possible.  You need a 2-inch or 4-inch
thick filter with at least a MERV-11 rating, not a plain old furnace
filter.  I use a full size furnace blower with a 20 x 25 inch air
filter over the intake.

3 - Wear a dust mask, or better yet a respirator.

I have my air cleaner plugged into a switched outlet that goes on with
the lights in my shop.  I have it on whenever I'm cutting or sanding
wood for a project.  I arranged the air flow such that the air moves
past me and then past the work and then into the air cleaner.

In the case that Richard Friedman describes, I'd put a fan in a window
opposite his open doorway.  The fan would blow into the room, past me,
past the piano (where it picks up the dust) and out the door.  And I'd
wear a mask too because the dust is very fine and I don't know what's
in it.

Regards from sunny upstate New York (85 degrees)
Craig Smith