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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The thinking on the effect of H2S on respiratory functions has
changed. <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-family:"Arial","sans-serif"'>Since the
1970s, the exposure limit for hydrogen sulfide (H<sub>2</sub>S) was 10 ppm
(8-hour TWA - time weighted average) and 15 ppm (STEL - short term exposure
limit). In 2010, the ACGIH revised the exposure limits for H 2 S to 1 ppm
(TWA) and 5 ppm (STEL). The basis and rationale for the changes can be
found in the 2010 ACGIH Documentation for H<sub>2</sub>S.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Arial","sans-serif"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-family:"Arial","sans-serif"'>The ACGIH has
documented the following information relating to the effects of H 2 S: <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Arial","sans-serif"'> <o:p></o:p></span></p>
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<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>1000-2000
ppm</span><span lang=EN-US style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
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border-left:none;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>Loss
of consciousness and possible death</span><span lang=EN-US style='font-family:
"Arial","sans-serif"'><o:p></o:p></span></p>
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border-top:none;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>100
– 1000 ppm</span><span lang=EN-US style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
</td>
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padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>Serious
respiratory, central nervous, and cardiovascular system effects</span><span
lang=EN-US style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
</td>
</tr>
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border-top:none;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>150-200
ppm</span><span lang=EN-US style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
</td>
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<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>Olfactory
fatigue</span><span lang=EN-US style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
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border-top:none;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>100
ppm</span><span lang=EN-US style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
</td>
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<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>Immediately
Dangerous to Life and Health (IDLH) concentration</span><span lang=EN-US
style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
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</tr>
<tr>
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border-top:none;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>5-30
ppm</span><span lang=EN-US style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
</td>
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<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>Moderate
irritation of the eyes</span><span lang=EN-US style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
</td>
</tr>
<tr>
<td width=145 valign=top style='width:108.9pt;border:solid black 1.0pt;
border-top:none;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>5-10
ppm</span><span lang=EN-US style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
</td>
<td width=493 valign=top style='width:369.9pt;border-top:none;border-left:
none;border-bottom:solid black 1.0pt;border-right:solid black 1.0pt;
padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>Relatively
minor metabolic changes in exercising individuals during short-term exposures</span><span
lang=EN-US style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
</td>
</tr>
<tr>
<td width=145 valign=top style='width:108.9pt;border:solid black 1.0pt;
border-top:none;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'><
5 ppm</span><span lang=EN-US style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
</td>
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<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>Metabolic
changes observed in exercising individuals, but not clinically significant</span><span
lang=EN-US style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
</td>
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border-top:none;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>5
ppm</span><span lang=EN-US style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
</td>
<td width=493 valign=top style='width:369.9pt;border-top:none;border-left:
none;border-bottom:solid black 1.0pt;border-right:solid black 1.0pt;
padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>Increase
in anxiety symptoms (single exposure)</span><span lang=EN-US
style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
</td>
</tr>
<tr>
<td width=145 valign=top style='width:108.9pt;border:solid black 1.0pt;
border-top:none;padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>5
ppm</span><span lang=EN-US style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
</td>
<td width=493 valign=top style='width:369.9pt;border-top:none;border-left:
none;border-bottom:solid black 1.0pt;border-right:solid black 1.0pt;
padding:0in 5.4pt 0in 5.4pt'>
<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'>Start
of the dose-response curve (short term exposure)</span><span lang=EN-US
style='font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
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</table>
<p class=MsoNormal><span lang=EN-US style='font-family:"Arial","sans-serif"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Arial","sans-serif";color:#1F497D'>Pat Coleman, PhD PEng</span></b><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> <br>
</span><span lang=EN-US style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>Pat.F.Coleman@aecom.com</span><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'> <br>
</span><span lang=EN-US style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>Manager of Process Technology - Wastewater Treatment<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>AECOM.</span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> <br>
<br>
</span><span lang=EN-US style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span lang=EN-US
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D'>T:
905.712.7025 Mississauga </span><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>(leave a message and it will be emailed to me wherever I am)<br>
</span><span lang=EN-US style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>T.</span><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:#1F497D'> 905.747.7595 Markham<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Arial","sans-serif";color:#1F497D'>C. 647.637.2898 </span><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><br>
</span><span lang=EN-US style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>www.aecom.com</span><span lang=EN-US style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'> </span><span lang=EN-US
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> </span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> digestion-bounces@lists.bioenergylists.org
[mailto:digestion-bounces@lists.bioenergylists.org] <b>On Behalf Of </b>Matt
Lorig<br>
<b>Sent:</b> Thursday, February 24, 2011 5:44 PM<br>
<b>To:</b> digestion@lists.bioenergylists.org<br>
<b>Subject:</b> [Digestion] Hydrogen sulfide - Biogas (Julio Eli Martinez)<o:p></o:p></span></p>
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<p class=MsoNormal>If you are using the gas only for cooking there is not
really much need to scrub the H2S. Keep in mind that it is very
corrosive so use plastic pipes,etc. <br>
<br>
H2S can actually be helpful in low tech applications as the smell lets you
know if you have leaks.<br>
<br>
Date: Thu, 24 Feb 2011 12:07:44 -0600<br>
From: "Amy and Jim Rankin" <<a
href="compose?to=ajrankin@hughes.net">ajrankin@hughes.net</a>><br>
To: "For Discussion of Anaerobic Digestion"<br>
<<a
href="http://us.mc782.mail.yahoo.com/mc/compose?to=digestion@lists.bioenergylists.org">digestion@lists.bioenergylists.org</a>><br>
Subject: Re: [Digestion] Hydrogen sulfide - Biogas<br>
Message-ID: <F761972DFB6C4622A2F5FE0F5EA3B1E7@RankinPC><br>
Content-Type: text/plain; charset="utf-8"<br>
<br>
<br>
"""""""""""""""""<br>
I am new on this list serve, I have a question regarding the danger of
H2S, I have been reading about this gas and its dangers, I am developing a
project in a rural community in Mexico, I'm helping to develop 5 tubular PE-
biodigesters, I am still working on solve the Hydrogen sulfide issue, I don't
want to put people's life on risk; so, any help on the manage or elimination
of Hydrogen sulfide on Bio-gas systems will be helpful, <br>
"""""""""""""""""""""""""""""""<br>
If you control the biogas appropriately, you will mitigate the risk of
the hydrogen sulfide. <br>
<br>
However, there are ways to scrub the biogas on the way out of the digester
(exposure to rusty steel wool, lathe turnings,shredded sheetmetal etc) or it
can be collected in the digester by admitting a small amount of oxygen to the
digester which causes the Sulfur to collect as less dangerous forms within
the digester, eventually passing out with the effluent. Sulfur has
become an important plant nutrient in these days of decreasing powerplant
sulfur emissions here in the USA and elsewhere in the developed world.
The amount of oxygen would have to be regulated to stay below the level where
the mixture becomes flammable. Not quite so simple a technology as the
poly tube digester you are working with. <br>
<br>
As part of your training for the operators of the digesters, you must
emphasize that the digester is a very dangerous place. Not that a poly
tube digester is somewhere a person might ever go. This is not only
because of hydrogen sulfide, but also because of the carbon dioxide and
methane. Every year or two, someone (and sometimes several
"rescuers" as well) is killed when they enter a pit or other
place where the biogas/manure gas has accumulated or is being liberated
rapidly enough to reach dangerous concentrations.<br>
<br>
Jim<br>
<br>
James R Rankin, DVM<br>
Cedarcrest Farms, Inc<br>
Faunsdale, Alabama USA<br>
<br>
Matt Lorig<br>
mattlorig@yahoo.com<o:p></o:p></p>
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