Monona Rossol on sun 26 may 96
Cynthia
I'm sitting here with plans for art buildings at two Universities--both involve
ceramics. I get paid to make sure stuff like you describe NEVER happens.
As John Baymore explains, ventilation requirements have changed over the years.
Now there is just no way around it--you need to extend the chimney to the roof
and probably about 4 feet above the roof line depending on the configuration of
the roof and other stationary objects nearby at roof level or above.
I'm not even going to ask if you are in a city or a rural area and what local
codes might apply.
You might get away with an unvented electric kiln in a big space like this if
you don't care much about your health. But a gas kiln is like having a bonfire
in the middle of your living room.
It is necessary to exhaust all the gases out of the space and into the
prevailing air stream above the building. If you were not on your own, but were
a school or public facility, there would even have to be secondary powered
ventilation system to capture the gases missed by the stack especially during
reduction.
Since most downdraft kilns have a damper at the entrance to the stack, you
should be able to get away without any other control over the rate of draw from
the stack. The strong temperature differential from the hot kiln to the cool
air at the top of the stack will create a hell of a pull especially toward the
end of the firing. The damper, if it is a good one, will take care of this.
Otherwise you need a draft regulation unit in the duct as well.
John Baymore's suggestion about the Nighthawk carbon monoxide detector is a good
one. Remember, the unit is set to preserve your life, not your health. Use the
"memory button" during a firing. If CO readings get in the range of 35 or 40
ppm, you need to start thinking about ways to get fresh air into the space. If
the alarm goes off--you really should abort the firing. The information on the
box has some very simplistic (and in my estimation misleading) information about
acute exposures. If you need information on chronic exposure, I have a data
sheet I can send you.
Any other questions you have, don't hesitate.
Monona Rossol, industrial hygienist with Arts, Crafts and Theater Safety
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