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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Thanks to everyone who weighed in on this discussion! Apologies that I couldn’t respond to most of you directly.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-family:"Calibri",sans-serif">I received many great pieces of advice that I’ll try (perhaps poorly) to summarize here:<o:p></o:p></span></b></p>
<ol style="margin-top:0in" start="1" type="1">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1"><span style="font-family:"Calibri",sans-serif">A few people recommended
<a href="https://www.amazon.com/Semiconductor-Industry-Wafer-Exhaust-Management/dp/1574447203">
this book</a>. It does a fantastic job of detailing incompatible chemistries and various point of use and centralized devices for scrubbing/oxidizing/cracking/abating. It does not say much about material compatibility.<o:p></o:p></span></li><ol style="margin-top:0in" start="1" type="a">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1"><i><span style="font-family:"Calibri",sans-serif">Fun fact #1</span></i><span style="font-family:"Calibri",sans-serif">: LLNL got its first scrubber about a year ago!
<o:p></o:p></span></li></ol>
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1"><span style="font-family:"Calibri",sans-serif">The community is in broad agreement that it’s better to have dedicated exhaust systems for different chemistries, but very few actually
<i>are</i>, because it’s expensive. Where labs are using >1 exhaust system, the +1 is typically for corrosives.<o:p></o:p></span></li><ol style="margin-top:0in" start="1" type="a">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1"><i><span style="font-family:"Calibri",sans-serif">Fun fact #2</span></i><span style="font-family:"Calibri",sans-serif">: LLNL has historically had 2 exhausts, one for fume hoods and
one for tools and gas cabinets, with crosstalk between the two. Given this is largely the wrong setup, we’ve been lucky to not have problems in decades of history of this facility, likely owing to our high airflow and lower-than-most utilization. I’d prefer
to do things right going forward, though!<o:p></o:p></span></li></ol>
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1"><span style="font-family:"Calibri",sans-serif">I learned about fluoropolymer-coated stainless steel (e.g.,
<a href="https://www.fabtechinc.com/PS_PSP.php">PSP</a>) as a duct material. Expensive at time of installation, but the most versatile by far, especially if exhaust streams can’t be ideally segregated.<o:p></o:p></span></li><ol style="margin-top:0in" start="1" type="a">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1"><span style="font-family:"Calibri",sans-serif">SS, FRP, PVC, and galvanized steel each have their place. SS and galvanized steel are suitable for heat exhaust and solvents, with SS
being the more premium option of the two.<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1"><span style="font-family:"Calibri",sans-serif">PVC and FRP are suitable for corrosives, with FRP being preferred for long runs and PVC suitable only for short runs from tool to trunk.
However, FRP is reportedly the most difficult to work with, and few vendors are still using it.<o:p></o:p></span></li></ol>
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1"><span style="font-family:"Calibri",sans-serif">There are different opinions on how important it is to separate (or scrub) the various different chemistries versus diluting them, and
how severe the problems <i>really </i>are in a research-scale fab, but ammonia reacting with halogens to form salts is universally recognized as problematic.<o:p></o:p></span></li><ol style="margin-top:0in" start="1" type="a">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1"><i><span style="font-family:"Calibri",sans-serif">Fun fact #3</span></i><span style="font-family:"Calibri",sans-serif">: LLNL has had SC-1 and SC-2 at the same fume hood for a few
decades. We’ll be investigating the ducts above the bench in the very near future for ammonium chloride deposits. Not to dismiss the concern, but my teammates (and more importantly, my predecessors) have never seen an airflow issue at this bench.<o:p></o:p></span></li></ol>
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1"><span style="font-family:"Calibri",sans-serif">Most facilities have redundant fans. I’ve heard everything from 1+1 to 5+1. Universally considered good practice.<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1"><span style="font-family:"Calibri",sans-serif">Several people referred me back to code and regulatory agencies. We’re under our emissions thresholds for Bay Area Air Quality Management
District and California Air Resources Board, so no abatement has been required (yet). That said, I’ve been talking with those folks for a couple of months about better-than-minimum abatement with the expectation that requirements in the Bay Area will only
grow stricter as time goes to infinity, and our utilization is expected to increase with time (and with this facility expansion).<o:p></o:p></span></li></ol>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Also, to the several folks to shared the wisdom to design with a long-term mindset, and to plan to do it right the first time – I’m 100% with you. With this fixed-budget expansion project,
I would rather end up with a shell of a building that has all the right utilities in place but needs to be filled in over time with modular cleanrooms and last-mile utility drops, rather than to have a fully built cleanroom with inadequate utilities supplied
to the building, improper materials/construction, or a 1/3 smaller footprint. I’m
<i>gradually</i> getting the building folks to come around to the idea.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Best,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Travis<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
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<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-family:"Calibri",sans-serif">From:</span></b><span style="font-family:"Calibri",sans-serif"> labnetwork <labnetwork-bounces@mtl.mit.edu>
<b>On Behalf Of </b>Iulian Codreanu<br>
<b>Sent:</b> Wednesday, February 26, 2025 5:03 AM<br>
<b>To:</b> labnetwork@mtl.mit.edu<br>
<b>Subject:</b> Re: [labnetwork] Combined or separate exhaust?<o:p></o:p></span></p>
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</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hi Travis,<br>
<br>
In the two cleanrooms I helped build I had a number of exhaust systems:<br>
-Two for the cleanroom itself<br>
-One for the gas room<br>
-One for the gas bunker.<br>
<br>
Each exhaust system has at least two fans for capacity and n+1 redundancy.<br>
<br>
Folks use different names for the two exhaust systems typically used for the tools and hoods in cleanroom but a simple way to look at it is by focusing on the fume hoods:<br>
-One is for corrosives; typically teflon-coated SS but I have plastic too (not my favorite)<br>
-One is for solvents; typically SS but I have seen galvanized steel too (not my favorite)<br>
<br>
When hooking up tools to the exhaust system you decide based on what kind of gases those tools will process; e.g. an evaporator ties to the solvent exhaust and a PECVD to the corrosive exhaust.<br>
<br>
You have to keep in mind your local codes and the input of the authority having jurisdiction. EHS may be a good resource to support your efforts to perhaps go above the minimum requirements; when designing/building those labs my mindset was that I was going
to live with them until I retired. We all know that it's easier/cheaper to put things in place when you build new rather than adding them later.<br>
<br>
Good luck!<br>
<br>
<br>
<br>
<span style="font-size:12.0pt"><o:p></o:p></span></p>
<pre>iulian Codreanu, Ph.D.<o:p></o:p></pre>
<pre>Director, Nanofabrication Facility<o:p></o:p></pre>
<pre>University of Delaware<o:p></o:p></pre>
<pre>Harker ISE Lab, Room 163<o:p></o:p></pre>
<pre>221 Academy Street<o:p></o:p></pre>
<pre>Newark, DE 19716<o:p></o:p></pre>
<pre>302-831-2784<o:p></o:p></pre>
<pre><a href="https://urldefense.us/v3/__https:/udnf.udel.edu__;!!G2kpM7uM-TzIFchu!0QeMy7maqRVZHHc6rUqyhh1ejrXBvMCijTxVekBjc6JEoecHsRLqCrK7UpSTt18bM7CCf7SdeuRCcTz4nIyv$">https://udnf.udel.edu</a><o:p></o:p></pre>
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<p class="MsoNormal">On 2/24/2025 9:23 PM, Massey, Travis wrote:<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Hi all,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">LLNL is planning a significant cleanroom expansion, and the question arose whether we
<i>need</i> separate exhaust for hoods and tools/gases, or if they can be combined into a single shared exhaust. Or do you have a single exhaust with 2+ exhaust fans pulling simultaneously, so there’s always
<i>some </i>exhaust air moving if one fan is down? The conventional wisdom around here has its share of holes, so I’m out to learn from the broader nanofab cleanroom community. How are your cleanrooms’ exhaust systems are configured, especially if you’ve
had to go down this cleanroom design rabbit hole?</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">I’m also broadly open
<i>any</i> other lessons learned regarding provisioning exhaust or other utilities – whatever you feel like sharing. Too much information during the design phase is far better than too little.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><br>
Thanks,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Travis Massey</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Center for Micro and Nano Technology (CMNT)</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Lawrence Livermore National Laboratory (LLNL)</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><br>
<br>
<o:p></o:p></span></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>labnetwork mailing list<o:p></o:p></pre>
<pre><a href="mailto:labnetwork@mtl.mit.edu">labnetwork@mtl.mit.edu</a><o:p></o:p></pre>
<pre><a href="https://urldefense.us/v3/__https:/mtl.mit.edu/mailman/listinfo.cgi/labnetwork__;!!G2kpM7uM-TzIFchu!0QeMy7maqRVZHHc6rUqyhh1ejrXBvMCijTxVekBjc6JEoecHsRLqCrK7UpSTt18bM7CCf7SdeuRCcSB_ZdvI$">https://mtl.mit.edu/mailman/listinfo.cgi/labnetwork</a><o:p></o:p></pre>
</blockquote>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
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