Edouard Bastarache Inc. on fri 1 dec 06
AUTHOR: Bob Hirtle; Kay Teschke; Chris van Netten; Michael Brauer
TITLE: Kiln Emissions and Potters' Exposures
SOURCE: American Industrial Hygiene Association Journal v59 no10 p706-14 =
O '98
The magazine publisher is the copyright holder of this article and it is =
reproduced with
permission. Further reproduction of this article in violation of the =
copyright is prohibited.
ABSTRACT
Some ten thousand British Columbia potters work in small private =
studios, cooperative
facilities, educational institutions, or recreation centers. There has =
been considerable
concern that this diffuse, largely unregulated activity may involve =
exposures to
unacceptable levels of kiln emissions. Pottery kiln emissions were =
measured at 50
sites-10 from each of 5 categories: professional studios, recreation =
centers,
elementary schools, secondary schools, and colleges. Area monitoring was =
done 76 cm
from firing kilns and 1.6 m above the floor to assess breathing zone =
concentrations of
nitrogen dioxide, carbon monoxide, sulfur dioxide, fluorides, aldehydes, =
aluminum,
antimony, arsenic, barium, beryllium, boron, cadmium, chromium, cobalt, =
copper, gold,
iron, lead, lithium, magnesium, manganese, mercury, nickel, selenium, =
silver, vanadium,
and zinc. Personal exposures to the same metals were measured at 24 =
sites. Almost
all measured values were well below permissible concentrations for =
British Columbia
work sites and American Conference of Governmental Industrial Hygienists =
(ACGIH)
threshold limit values (TLVs) with the following two exceptions. A =
single firing duration
(495 minute) acrolein measurement adjacent to an electric kiln (0.109 =
ppm) exceeded
these guidelines. One 15-minute sulfur dioxide measurement collected =
adjacent to a
gas kiln (5.7 ppm) exceeded the ACGIH short-term exposure limit. The =
fact that
concentrations in small, ventilated kiln rooms ranked among the highest =
measured
gives rise to concern that unacceptable levels of contamination may =
exist where small
kiln rooms remain unventilated. Custom designed exhaust hoods and =
industrial heating,
ventilating, and air-conditioning systems were the most effective =
ventilation strategies.
Passive diffusion and wall/window fans were least effective.
(.......)
VENTILATION
Ventilation is generally recommended to control emissions from kilns.
Unfortunately, some of the ventilation strategies observed in this study
proved ineffective. Domestic wall/window fans, for example, appeared=20
to have minimal impact on contaminant concentrations.=20
Exhaust slots around kiln lid perimeters were limited in their ability =
to=20
capture rapidly rising contaminants at higher kiln temperatures.
Certain oversights in design or application likely resulted in =
compromised
ventilation performance at a number of sites. The quantity of =
replacement=20
air may have been inadequate or the position of the air intake may have=20
resulted in airflow patterns that failed to optimize the capture of kiln =
emissions.=20
Because of their size and location, some exhaust vents were not specific =
for kiln emissions, but acted more as general room exhausts, allowing=20
the mixing of kiln emissions with room air.
Passive ventilation appears at least as effective as four other =
ventilation
strategies (direct exhaust, overhead exhaust, wall/window fans, and slot =
exhausts).
This may reflect conditions specific to those sites where passive =
ventilation
was observed: low emissions levels, large dilution volumes, or natural =
airflow
resulting in a reduced needfor additional ventilation.
Where kilns were old and leaky, lids left ajar, or peep holes open, =
direct
venting through the bottom of the kiln was unable to prevent the escape =
of=20
emissions into the kiln room. For negative pressure (direct venting) =
systems=20
to be effective, it has been recommended that the fan should be near the =
exhaust end.
Whether measured exhaust efficiency of directly venting kilns was =
compromised=20
by fan placement of duct length is not certain.
Despite some variation related to size, design, and placement, the use =
of
exhaust hoods was found to be one of the more effective ventilation =
strategies.
Because certain exhaust strategies (e.g., wall exhausts) were not in =
common use,=20
this study was limited in its ability to report their relative =
effectiveness with=20
certainty.
Later,
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://perso.wanadoo.fr/smart2000/index.htm
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