I can't think of anything that would work on coal dust, other than a
vaccuum cleaner or heat from a heat gun to convert the coal into CO2.
Maybe try vaccuuming first, and see what that does.
Then, if you have an electric leaf blower, I'd try that next.
Then, I'd try heating the wall in a small area with a heat gun (or
propane torch) to coax the coal into becoming CO2.
And, ultimately, if nothing works well, you can buy a "block filler"
paint made specifically for painting concrete blocks. This is a thick
paint that fills the surface porosity of concrete blocks to make for a
smoother, more attractive surface.
Nasty stuff, I would look to seal all of it in some way. Putting fire to
coal dust sounds like an explosive situation. Blowing coal dust around
isn't too good for your health either (black lung). Think of drywall
dust but 10x worse.
Wash or vacuum off the loose stuff (may ruin your vacuum though) then
parge the walls. Prime and paint if you wish. The stuff on the floor
floor could be shoveled up and disposed of, bury or burn *outside*, and
then the floor mopped. I don't know if parging would hold up on the
floor so maybe a cheap tile job (so called 'first run' tiles are as
little as $1 each) would seal the floor. Good place to practice if you
have never tiled before, especially using 'first run' as they are not
uniform in size.
After cleaning per Greg Z, a couple of coats of a latex paint applied
with a long roller should penetrate into the blocks and seal them
Even better would be to clean the walls using a pressure washer and
some means of catching the dirty water, and then allowing to dry
thoroughly for several days, and then applying paint using a pressure
washer to get the paint deep into the cinder blocks. You don't say
that the wall is "wet", so I'm assuming that water seepage is not a
I would scrape the heavy stuff off walls and floors, pick up all the
debrs as best as possible, then pressure wash everything.....
I lived in a home converted to natural gas from coal heat and have
been in many homes that were converted.
Although there was some loose coal dust in basement the coal cellar
rooms were always clean so it must not have been hard to clean
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