One of my jobs in life is helping design clean rooms. If you put the
DC outside - say a 1200 CFM jobby - and your wood shop is in the
basement - you will create a partial vacuum in the basement sucking a
lot of air down the chimney - would probably extinguish any open cycle
gas furnace or water heater - worst if it did not extinguish the flame
- would have build up of at least CO2 and maybe CO.
If you put it in a closet in the basement - air still must come out of
the closet and it will have particles in the air. Guess you could put
a bunch of HEPA filters in one of the walls and catch the vast majority
of the fines.
All of life is a trade off - if you use some of the finer mesh bags it
probably will not be a problem - unless you are one heck of a wood
There seems to be confusion in many of the replies about where air comes
from and goes. The air being heated and circulated comes through the
furnace ducting, and may or may not include air from/to the basement. In
the case of my furnace, combustion air comes from the room the furnace is
in, and is vented to a chimney when it leaves, taking combustion products
with it. Combustion air does not circulate through the house unless you
have a leak. If that happens, you will smell it and should get it fixed
I ran a dust collector in the same basement room as the furnace for years,
with no problems. I did have the dust collector as far from the furnace as
possible. I also had an air cleaner with 3 levels of filtering; the initial
furnace filter was the only one that ever had to be cleaned or replaced.
Duane said that even with the air being drawn from elsewhere there are
inevitably leaks in the ductwork. Our furnace operates like you said,
air drawn from the house into the furnace with the furnace being vented
by a chimney. I think the setup will be the DC in the basement with the
furnace inside a closet that is vented outside.
Please do not overlook the information about pressures pointed out by
Butch. The DC creates a negative pressure to collect the dust from
your saw or planer or whatever. If the DC is in the same area as the
furnace or water heater, you need to restore the exit air from that DC
back into the room to equalize the pressure. If you vent the exit air
to the outside, you effectively keep a negative pressure in the shop
anytime the DC runs. If the furnace is on at the same time, flue gases
can be sucked back down the chimney rather than going their normal flow
and therefore cause you extreme danger for CO poisoning. DCs can be
vented outside in climates where no furnace is needed or where the
furnace is in some other part of the house.
I don't think this is an issue, I may not be understanding it correctly
though. The setup is an unheated garage/workshop where the door is
always open when I'm working. The furnace is in an adjacent area that
extends all the way under the house which is very well ventilated. So
the shop would be at negative pressure because that's where the air is
being sucked from but that is wide open, and the DC would be vented
outside relieving the positive pressure the unit itself would generate.
I am right here ?
The exhaust from the DC should be clean enough to not worry about
an explosion hazard unless you shake a lot of dust into the air
when you are emptying it.
Over the years folks here on rec.WW have done the arithmetic and
shown that normal woodworking operations, dust collection and so
on do not generate dust fast enough to create an explosive
atmosphere under steady state conditions.
However if dust accumulates somewhere and then lets go all
at once the assumption of steady state conditions is violated
and the concentration fo air could momentarily reach the
lower inflammible limit--the whumphf threshold.
On 7 Mar 2005 13:59:06 -0800, email@example.com wrote:
ayup. one way you could approach that limit with home shop dust
collection equipment is to use your DC to suck up a big pile of
sawdust. 'course, you still need a source of ignition- which could be
a bit of metal in the pile hitting the impeller. the most likely
result would be a smoldering fire in the bag, but that's enough to
take out your house. so be careful....
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