Edouard Bastarache Inc. on thu 23 oct 03
Hello,
I-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
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.
II-Texts based on the same article:
A-Carbon monoxide:
It was one of the many contaminants studied.
Carbon monoxide was detected at 26 sites.
At 10 of the sites where CO was detected, only greenware was being bisqued.
Eight sites were firing only glazed bisque ware.
The remaining eight sites were firing both.
The two highest 1-minute spikes (95 and 68 ppm) occurred when exhaust rates
for gas kilns were damped to diminish the intake of fresh air, balance
internal temperature, limit the availability of oxygen inside the kiln, and
create a chemically reducing environment. Fifteen-minute average
concentrations around these peaks were 82 and 66 ppm, respectively.
Measurable emissions were noted between 150 and 750°C, with most detected
values
occurring at temperatures between 200 and 600°C.
The highest average carbon monoxide concentration measured in this study,
averaged over 645 minutes, was 7 ppm. This concentration was lower than the
35
ppm Quebec's exposure limit and previously reported values of 40 ppm
(Lange,A.E. et al.) and 59 ppm (Reist, P.C.).
Blood carboxyhemoglobin levels in adults exposed to concentrations of 10 ppm
for 4 to 12 hours do not exceed 2%-a level that has not been shown to cause
health problems
in normally healthy human adults (Amdur, M., et al.).
Heavy cigarette smokers may have up to 9% carboxyhemoglobine while 20% was
reported among some cigar smokers.
The highest 15-minute average exposure (82 ppm) was below Quebec's
short-term exposure limit of 200 ppm and a reported measurement of 113 ppm
(Reist P.C.)
Average carbon monoxide concentrations were not found to vary significantly
between gas and electric firings. This was surprising because the electric
firing is
considered an oxidation firing, where one would expect carbon to be oxidized
to
carbon dioxide. In contrast, one would expect considerable carbon monoxide
to be
generated during the reduction phase of a gas firing when excess oxygen is
not
available. It may be that these expectations were not realized for the
following reasons.
(1) There is considerable awareness and concern regarding the potential for
noxious
emissions from gas burners, and potters are likely to ensure professional
installation
and inspection of gas and ventilation systems. Electric kilns are usually
installed by the
potter and levels of ventilation similar to those used with gas kilns are
not usually
considered necessary.
(2) The presence of carbon monoxide around electric kilns suggests that
there is
insufficient oxygen, at least in some firings, to complete the oxidation
process.
B-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
to have minimal impact on contaminant concentrations. Exhaust slots around
kiln lid perimeters were limited in their ability to 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 air may have been inadequate or
the position of the air intake may have resulted in airflow patterns that
failed to optimize the capture of kiln emissions. Because of their size and
location, some exhaust vents were not specific for kiln emissions, but acted
more as general room exhausts, allowing 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 need for 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
emissions into the kiln room. For negative pressure (direct venting) systems
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 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, this study was limited in its ability to report their relative
effectiveness with certainty.
III-For a comprehensive report on the toxicology of Carbon Monoxide go to:
http://perso.wanadoo.fr/smart2000/monoxyde_de_carbone.htm#English
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
Louis Katz on thu 23 oct 03
Thanks,
Louis
Ron Roy on mon 27 oct 03
Just in case anyone is feeling safe after reading this - remember - you
need to think worst case scenario for all our firings.
Wind direction has a profound influence on ventilation systems for starters.
Amount of contaminants in any particular clay batch is a big factor and you
cannot tell what the levels are in any particular clay - from bag to bag
and batch to batch.
CO poisoning depends on a number of factors for instance - how much carbon,
what size is the room, is the ventilation working properly, is the wind
outside helping the system or working against it - and where is the
replacement air coming from.
It does not matter how many tests are done - it is the exception that we
must be concerned about - so treating every firing as a worst case scenario
is the only safe way.
You will be amazed at how many people are done in each year by carbon
monoxide poising - by accident - not to mention the adverse health effects
by even lower than permissible levels of CO over time.
RR
>I-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
>
>
>
>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 industria=
l
>heating,
>
>ventilating, and air-conditioning systems were the most effective
>ventilation strategies.
>
>Passive diffusion and wall/window fans were least effective.
>
>
>
>II-Texts based on the same article:
>
>
>
>A-Carbon monoxide:
>
>It was one of the many contaminants studied.
>
>
>
>Carbon monoxide was detected at 26 sites.
>
>At 10 of the sites where CO was detected, only greenware was being bisqued.
>
>Eight sites were firing only glazed bisque ware.
>
>The remaining eight sites were firing both.
>
>The two highest 1-minute spikes (95 and 68 ppm) occurred when exhaust rates
>for gas kilns were damped to diminish the intake of fresh air, balance
>internal temperature, limit the availability of oxygen inside the kiln, and
>create a chemically reducing environment. Fifteen-minute average
>concentrations around these peaks were 82 and 66 ppm, respectively.
>
>Measurable emissions were noted between 150 and 750=B0C, with most detected
>values
>
>occurring at temperatures between 200 and 600=B0C.
>
>The highest average carbon monoxide concentration measured in this study,
>
>averaged over 645 minutes, was 7 ppm. This concentration was lower than the
>35
>
>ppm Quebec's exposure limit and previously reported values of 40 ppm
>(Lange,A.E. et al.) and 59 ppm (Reist, P.C.).
>
>Blood carboxyhemoglobin levels in adults exposed to concentrations of 10 pp=
m
>for 4 to 12 hours do not exceed 2%-a level that has not been shown to cause
>health problems
>
>in normally healthy human adults (Amdur, M., et al.).
>
>Heavy cigarette smokers may have up to 9% carboxyhemoglobine while 20% was
>reported among some cigar smokers.
>
>The highest 15-minute average exposure (82 ppm) was below Quebec's
>short-term exposure limit of 200 ppm and a reported measurement of 113 ppm
>(Reist P.C.)
>
>Average carbon monoxide concentrations were not found to vary significantly
>
>between gas and electric firings. This was surprising because the electric
>firing is
>
>considered an oxidation firing, where one would expect carbon to be oxidize=
d
>to
>
>carbon dioxide. In contrast, one would expect considerable carbon monoxide
>to be
>
>generated during the reduction phase of a gas firing when excess oxygen is
>not
>
>available. It may be that these expectations were not realized for the
>following reasons.
>
>(1) There is considerable awareness and concern regarding the potential for
>noxious
>
>emissions from gas burners, and potters are likely to ensure professional
>installation
>
>and inspection of gas and ventilation systems. Electric kilns are usually
>installed by the
>
>potter and levels of ventilation similar to those used with gas kilns are
>not usually
>
>considered necessary.
>
>(2) The presence of carbon monoxide around electric kilns suggests that
>there is
>
>insufficient oxygen, at least in some firings, to complete the oxidation
>process.
>
>
>B-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
>to have minimal impact on contaminant concentrations. Exhaust slots around
>kiln lid perimeters were limited in their ability to 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 air may have been inadequate o=
r
>the position of the air intake may have resulted in airflow patterns that
>failed to optimize the capture of kiln emissions. Because of their size and
>location, some exhaust vents were not specific for kiln emissions, but acte=
d
>more as general room exhausts, allowing 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 need for 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
>emissions into the kiln room. For negative pressure (direct venting) system=
s
>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 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, this study was limited in its ability to report their relative
>effectiveness with certainty.
>
>
>
>III-For a comprehensive report on the toxicology of Carbon Monoxide go to:
>
>
>
>http://perso.wanadoo.fr/smart2000/monoxyde_de_carbone.htm#English
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
=46ax: 613-475-3513=20
Edouard Bastarache Inc. on mon 27 oct 03
Hello Ron,
Exemples of serious and important carbon monoxide situations :
I-In one of the steel plants I work for as a consultant we use daily
200,000 cubic feet of a gas having the following composition :
35% carbon monoxide
55% hydrogen
10% a mixture of nitrogen and carbon dioxide.
This gas mixture is used to reduce iron ore pellets before they are put
into 150 ton electric furnaces in order to make mild steel.
We call the furnaces (2) where reduction takes place: « reduction plants » .
You have to climb 345 stairs to get to the top.
It reminds of the process used to fire pots in reduction.
The gases are recycled.
We have CO detectors all over the place and "CO squads"
always ready to intervene in conjunction with the medical department.
II-Another company produces huge amounts of carbon monoxide in reducing
ilmenite ore to iron and titanium dioxide slag in 8 X 90 ton reduction
furnaces
using coal and electricity, coal being the reducing agent.
In the kilns they put 1 layer of ilmenite and 1 of coal in a repeated
manner.
3 X 1-yard thick electrodes bring energy to this layered mixture
The CO is recycled into energy used somewhere else in other processes.
So, as you may imagine, we had to learn how to deal with these huge amounts
of carbon monoxide on a daily basis, and we are well aware of the health
effects.
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
----- Original Message -----
From: "Ron Roy"
To:
Sent: Monday, October 27, 2003 3:14 PM
Subject: Re: Clean air and carbon monoxide
Just in case anyone is feeling safe after reading this - remember - you
need to think worst case scenario for all our firings.
Wind direction has a profound influence on ventilation systems for starters.
Amount of contaminants in any particular clay batch is a big factor and you
cannot tell what the levels are in any particular clay - from bag to bag
and batch to batch.
CO poisoning depends on a number of factors for instance - how much carbon,
what size is the room, is the ventilation working properly, is the wind
outside helping the system or working against it - and where is the
replacement air coming from.
It does not matter how many tests are done - it is the exception that we
must be concerned about - so treating every firing as a worst case scenario
is the only safe way.
You will be amazed at how many people are done in each year by carbon
monoxide poising - by accident - not to mention the adverse health effects
by even lower than permissible levels of CO over time.
Lee Love on tue 28 oct 03
The heating of our house is done with two small, rather high tech
kerosene heaters (they have blowers and are operated by a built-in
computer.) We looked around locally for smoke alarms and could not find
any carbon monoxide detectors. The smoke alarms are expensive here in
Japan.
So we asked a friend to send us one of each from
Minnesota. We slept much better after installing these in our house.
For the summer, I put the carbon monoxide detector in the
studio. It is interesting: the wood stove can be smoking up the space
pretty bad but not set off the carbon monoxide detector. But the wood
kiln, without any visible smoke, can set it off.
Lee In Mashiko, Japan
http://Mashiko.org
Web Log (click on recent date):
http://www.livejournal.com/users/togeika/calendar
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