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common
questions:
Here
is some info that may be helpful on the subject of air
cleaners.
To determine the size or required air flow, use this
formula: Volume of your shop (Length x width x Height)
times Number of air changes per hour (typically 6 -
8) divided by 60. This will give you an answer in Cubic
Feet per Minute which is how air cleaners are measured.
Most air cleaner manufacturers rate the CFM of the fan
only but there are losses due to the filters. If you
are building your own or if the air cleaner you are
purchasing rates only the fan, figure you will lose
about 25 - 40% for filtering losses.
As important as the air cleaner size is how and where
you mount it.
Try to mount at about 8-10 feet above the floor (no
lower than 6' or 2/3 of the floor to ceiling distance
if less than 8' ceiling)
Mount along the longest wall so the intake is approximately
1/3 the distance from the shorter wall. Mount no further
than 4-6 inches from the wall.
The exhaust is the largest determiner of the circulation
pattern. You are trying to encourage circulation parallel
to the floor/ceiling. The exhaust is the clean air so
that is what you want to position yourself in if you
are looking for health benefits. If the dust has to
pass your nose to get to the air cleaner, you get no
benefits.
If you have an odd shaped shop, two smaller units may
be better than one large one.
A couple of other thoughts. Do not rely on an air filter
to act as a dust collector. Its purpose is to keep airborne
dust in suspension and reduce airbourne dust as quickly
as possible. Use a smoke stick (or a cigar) to observe
and maximize circulation. Use a secondary fan to direct
air to the intake if necessary. Also, consider that
a standard 24" floor fan moves a lot of air and in some
shops just positioning it in a doorway with a window
or other door open can accomplish as much or more than
an air cleaner. It's all in the circulation patterns.
Finally, if you are looking for health benefits, you
will not find any air cleaner manufacturer that makes
health claims. No air filter will take the place of
a respirator if health is a concern.
- Howard Acheson
Last
winter I was sanding some oak in my shop (garage). And
even with a small exhaust fan and a bag on my sander,
I soon noticed the air filled with dust so bad I couldn't
see! Dust masks are no help when it's like this. I took
my trusty 24" box fan and duct taped the inlet down
to 20 x 20 for a furnace filter. 2 bungee cords later,
I had improvised a crude dust filter. Later the layer
of dust on the filter was amazing. It's not as effective
as a fancy commercial unit, but better than nothing.
Box fans don't suck very hard, so use the kind of filters
with the stuff that looks like blue fiberglass (really
cheap). The filter cuts airflow down about 50%, but
still effective in a 2 car garage. Set it to suck away,
and blow in a circle.
- Harold Groves
Most
of these units (the kind that hangs from the ceiling)
are the same. Blower, external filter and a 3 pocket
internal filter. The Grizzly I have is made in Taiwan
and is almost identical to the other Taiwan models I've
seen. You can get 3 micron filters for these, but that
puts a load on the fan and can reduce life span. Try
to get the highest CFM rating that you can. Mine moves
510 CFM and is not noisy. The more CFM the bigger the
blower and the bigger the noise. How big is your shop?
Mine is 20' x 26' x 7'. You also don't want to put the
unit in a corner. It will re-circulate the same air.
Try and find a place in the center or along the longest
wall to mount the unit. That will draw on the largest
volume of air in the shop.
- Bob N
With
these units there are a couple of things to think about.
First they are not dust collectors they are air cleaners.
The idea is to take out as much of the harmful very
small dust particles that cause you health problems.
You want to get a unit that takes out down to 1 micron
particles. The bad stuff is the very small stuff that
can get far into the lungs and cause many many issues.
The second is the flow rate. Calculate the total volume
of your shop. Length width height, then buy a air cleaner
that will replace that volume in a few minutes time
a 20 x 20 by 8 ft shop is 3200 ft3, a 500 cfm air cleaner
takes about 6 1/2 minutes to clean the total volume,
but it is not totally efficient. I would assume about
70%. That means that you would be breathing bad air
for about 10 minutes worst case with a 500 cfm unit
in that size shop. A 1000 cfm unit would be about 5
minutes better, but only you know what your needs are.
The comment about in the center of the shop is good.
I would place it nearest the largest source of fine
dust. That is where you do most of the sanding. The
larger tools make lots of chips and less small dust.
Another good thing to do is a sanding station that is
hooked to the main DC system to keep as much as possible
out of the air in the first place.
- Lou Williams
Get
a dust collection system together... or at least have
a vertical, double bag system on rollers until you do
get a system.
- Robert Walker
Do
not forget the dust . . . up front sacrifice some tools
for a really good dust collection setup. Oneida, cyclone
filter combination unit. Maybe add a room air re-circulation
ceiling unit as well. Both are well worth it.
- C. Scott
I’m
just finishing up a 20 x 24 shop. Before pouring the
concrete, try to place your table saw and put 1 1/2"
plastic conduit to where it will be needed at the saw
any perhaps any other area where you might need power
away from a wall. Also, I put 4" schedule 40 plastic
pipe under the concrete to where I need dust collection
at my table saw. You can save a lot of inconvenience
later by doing this now. Also, besides my lighting receptacles
in the ceiling, I also placed two outlets in the ceiling
controlled by a wall switch for the addition of a ceiling
air cleaner later.
- Daniel Stuckey
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