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HI Barbara
Before I retired a couple of years ago, my day job was as an
Occupational Health and Safety person. A lesson I learned more than
once is that designing effective exhaust ventilation systems is
difficult and can be quite expensive. Here are a few things to keep
in mind:
- There is a big, big difference between sucking and blowing air.
Its much easier to blow air where you want it than to effectively
exhaust a process. Lots of things interfere with good exhaust
ventilation. For example, every right turn in the duct work reduces
the air flow by 40-50 % so keep ducts as straight as possible. Longer
ducts reduce air flow. Flexible duct design causes turbulence and
reduces air flow significantly. Flex duct frequently has lots of
twists and turns, each one detracting from the exhaust efficiencyy.
Just because they did it at the factory next door does not mean it is
good.
- The hood, hose or other intake needs to be as close as possible to
the source of contamination. 90% of the velocity of exhaust
ventilation is lost in 1 diameter from the entrance. That means if
you have a 4 inch exhaust duct hose exhausting air at1,000 feet per
minute at the hose face, 4 inches out, you will only have a velocity
of 100 fpm. So get your work close to your hood or vice versa or you
will not have enough velocity to capture and transport the
contaminants.
- Its very unlikely that you are producing fumes, vapors, or
particulate at levels that are a significant health hazard. We tested
a lot around hand welding in electronics assembly and never found
dangerous of lead or other metals. That is because the melting point
is far enough below the boiling point where lots of fume would be
given off. Kilns are a horse of a different road clearance. The
particles given off by polishing, hand sanding etc are usually not a
size that would penetrate the body's defense systems and cause
chronic health problem.
- You could probably filter the air and return it to your work room
rather than exhausting it to the outside and do just as well. For
toxic work products, outside ventilation is needed, for nuisance
dusts and such, filtering ad return is probably adequate.
- There is ventilation/filter equipment available. I have not been
looking at this kind of stuff for several years so I 'm not sure
whats out there, I did find this at Lab Safety Supply Co.
http://tinyurl.com/65epe7
a portable fume extractor. I don't know the cost of anything about
it but it looks like it could be used for much of what we do. Or you
might think about using a vacuum cleaner for specific operations-
buffing sanding etc.
- I personally use a 3M Co dust fume and mist respirator (one of the
paper things) some of the time. I have a plan to set up a shop vac
to capture particulate from polishing and buffing, more for
housekeeping than for health reasons.
Hope this helps. Feel free to contact me off line if you have any
questions and I will try to answer them.
Jim
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