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Dan,<br>
We do not presently use these gases.<br>
I have been considering C5F8 as potential etch<br>
replacement if California imposes stringent controls on <br>
select freons due to their very high global warming CO2 equivalent
values.<br>
I expect I uncovered the same info you already have.<br>
<br>
1. Re C5F8 <br>
I found no indication that this gas is flammable.<br>
Praxair, Matheson, Linde and Air Liquide all list LC50 (1hr): 1124ppm<br>
but don't define reference for this info<br>
<br>
TGO "Class II" is defined as 200ppm - 3000ppm<br>
CFC "Toxic" Gas is defined as LC50 200ppm - 2000ppm<br>
Gas cabinet is required for TGO "ClassII" or CFC "Toxic".<br>
<br>
I would put C5F8 in a gas cabinet.<br>
<br>
-----<br>
2. C4F6<br>
definitely flammable but limited and inconsistent toxicity data<br>
A single source cited LC50 667ppm (4 hours, this is usually listed as 1
hour)<br>
<br>
I would consider C4F6 in a gas cabinet; <br>
I would seek additional info to support a decision either way<br>
<br>
-----<br>
3. CH2F2<br>
I found a single LC50 of 520,000ppm (4hour)<br>
and many TWA (8hr) > 1000ppm.<br>
This has been evaluated as a non-ozone depleting refrigerant<br>
for many years with some concerns about its flammability.<br>
<br>
I would handle like methane. I would not place in a gas cabinet.<br>
<br>
Of course all the usual disclaimers apply -<br>
not the opinion of University of California blah blah blah<br>
this is simply my personal evaluation,<br>
your local AHJ (Authority Having Jurisdiction) makes the call<br>
<br>
Good Luck and enjoy the snow,<br>
Bill Flounders<br>
UC Berkeley<br>
<br>
<br>
<br>
Dan Woodie wrote:
<blockquote
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<div>Hello from the white north,</div>
<div> </div>
<div>We are working on adding several of the more unusual
fluorocarbon gases to our Oxford 100 tool and we are having a hard time
getting clear information on proper handling and storage of some of the
gases. Specifically we are looking at adding:</div>
<div> </div>
<div>Difluoromethane (CH2F2)</div>
<div>Hexafluorobutadiene (C4F6)</div>
<div>Octofluorocyclopentene (C5F8)</div>
<div> </div>
<div>Unlike the more common fluorocarbons such as CHF3, CF4, C4F8,
these are all flammable, and the last two are also listed as toxic.
MSDS information on them is also light as they are fairly new materials
and most do not have TLV values set yet. Some sources
are indicating that the C5F8 does not need to be in a gas cabinet, but
a review of the MSDS makes me hesitant to follow that. Is anyone else
using this material and if so, how do you handle it? Thanks in advance
for your collective wisdom.</div>
<div> </div>
<div>Dan</div>
<div> </div>
<div>Dan Woodie</div>
<div>Lab Use Manager</div>
<div>Cornell NanoScale Facility</div>
<div>250 Duffield Hall</div>
<div>Ithaca, NY 14853-2700</div>
<div>(607)254-4891</div>
<div> </div>
<div> </div>
<div> </div>
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