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<div>I agree with Noah. Any potential exposure to HF is bad news. <br>
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Sent from my iPhone</div>
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On Mar 4, 2017, at 8:03 AM, Noah Clay <<a href="mailto:nclay@upenn.edu">nclay@upenn.edu</a>> wrote:<br>
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<div>Hi Sandrine,</div>
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<div>We have a 193nm excimer laser micromachining system in our cleanroom and went through a similar exercise. </div>
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<div>We concluded that even though OSHA or NIOSH limits would indicate that a gas cabinet is unnecessary, that housing the ArF cylinders in an exhausted enclosure is a safer/better option. Since the laser requires frequent purges/refills, placing the cylinder
near the cabinet is a must - therefore, it needed to be placed in an adjacent service chase. And so, we reasoned that:</div>
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<div>1. Housing F2 gases directly in the recirc path (no gas cabinet) was not an option.</div>
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<div>2. Shutting down the gas with with a TGMS interlock was required since</div>
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<div>3. We perceived inherent difficulty in diluting a full cylinder release, as might be the case with a standard gas panel that could not be shut down by our TGMS.</div>
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<div>4. Our researchers would be wielding pitchforks if they were exposed to high levels of F2, even if we explained it was permissible.</div>
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<div>I hope this helps.</div>
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<div>Best,</div>
<div>Noah</div>
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<div>Noah Clay
<div>Director, Quattrone Nanofabrication Facility</div>
<div>University of Pennsylvania </div>
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On Mar 3, 2017, at 14:28, Sandrine Martin <<a href="mailto:sandrine@umich.edu">sandrine@umich.edu</a>> wrote:<br>
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<div dir="ltr">Hello,
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<div>There are a few individual labs here at the University of Michigan that have excimer lasers and use F2 premix gases with 0.1 or 0.2% F2. So far, these gases have been installed in gas cabinets. We are now involved in a new installation and are getting
some push back about the need for a gas cabinet. </div>
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<div>The argument is made using the Compressed Gas Assoc Pamphlet P-20 Standard for Classification of Toxic Gas Mixtures (2009) that apparently states that, if the LC50 value is over 5,000ppm, the gas mixture is not considered toxic. </div>
<div>Pure F2 is listed with a LC50 (rat, 1h) at 185ppm. </div>
<div>At 0.2% F2, the calculated LC50 is then 92,500ppm, well above the 5,000ppm threshold and the premix is no longer considered a toxic gas. (it also has an NFPA rating of "1" in health on the MSDS)</div>
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<div>Since the mixture is not toxic and the F2 concentration is <1%, EH&S concludes that a gas cabinet is not required.<br>
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<div>However, considering that the F2 PEL is 0.1ppm and IDLH 25ppm, it still seems that a gas cabinet would be the safest option and the best solution.</div>
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<div>Has anybody gone through similar discussions? </div>
<div>If you have a lab with a fluorine premix gas, is it in a gas cabinet? If not, what type of space is it in, and what kind of ventilation and gas detection are in place?</div>
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<div>Thanks</div>
<div>Sandrine</div>
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<div>-- <br>
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