From: Andy Glode <andy.glode**At_Symbol_Here**UNH.EDU>
Subject: Re: [DCHAS-L] SF6 fume hood certification
Date: Fri, 12 Nov 2021 14:33:16 +0000
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Message-ID: BL3P223MB03530219940CF701BBC7BD398A959**At_Symbol_Here**BL3P223MB0353.NAMP223.PROD.OUTLOOK.COM
In-Reply-To <2F3F79D1-23B2-4496-978D-E556D16F09D6**At_Symbol_Here**>

Hi Ralph,

Thanks for raising this issue! The promise of the SF6 tracer gas test is that PPB concentrations of SF6 escaping from a hood will be detected accurately. However, I agree the tracer gas portion of the ASHRAE 110 test seldom delivers actionable information. In my experience with hundreds of ASHRAE 110 tests performed at UNH, none of our hoods have failed the tracer gas portion of the test, including tests done on our legacy hoods that pre-date ASHRAE 110. Other portions of the test have highlighted problems that affect hood performance or could undermine safe use, so the suite of tests is valuable to me. Recent literature on the subject (Ahn et al, "A new quantitative method for testing performance of in-use laboratory chemical fume hoods" 2015, and Smith, "Determination of suitable replacement of SF6 when used as a tracer gas in accordance with ANSI/ASHRAE Standard 110" 2020) raises several fundamental questions: is the SF6 tracer test consistent? Is it able to detect failur!
es in hood containment? Is a tracer gas test necessary when field-testing a hood or are other field tests adequate in identifying performance issues?

Please see my answers to your questions below.


Andy Glode, MS, CIH
Director, Office of Environmental Health and Safety
University of New Hampshire

-----Original Message-----
From: ACS Division of Chemical Health and Safety On Behalf Of Ralph Stuart
Sent: Friday, November 12, 2021 7:45 AM
To: DCHAS-L**At_Symbol_Here**Princeton.EDU
Subject: [DCHAS-L] SF6 fume hood certification

CAUTION: This email originated from outside of the University System. Do not click links or open attachments unless you recognize the sender and know the content is safe.

With COP 26 finishing up, those of us involved in assessing fume hood performance are thinking (again) about the use of SF6 as a tracer gas in fume hood evaluations (SF6 has 22,800 times the greenhouse gas potential of CO2). With this in mind, I have a couple of questions for the list:

1. Have CHAS members investigated alternatives to testing every fume hood using the ASHRAE 110 tracer gas test as written, using SF6 as the tracer gas?
AG: Yes, I have investigated alternatives, but there is little agreement on the best approach. I am very concerned there is limited value in the test and I am very concerned about the environmental impact of the test.

2. Has anyone changed their fume hood acceptance protocol to try to reduce the amount of such tests that are conducted for climate impact mitigation purposes?
AG: I have not formally changed our acceptance criteria, but I am actively exploring options to move away from the SF6 test.

3. Has anyone calculated the relative climate impact of doing a commissioning test of a hood using SF6 relative to the lifetime climate impact of the energy required by that hood?
AG: No, but this would be very interesting.

My personal opinion is that the test as written was designed to address specific design challenges associated with fume hoods when the standard was written in 1985. And it is based on a rather stilted scenario (a single user in a specific location with chemistry which is properly located in the hood). In my experience, essentially all hood installations since 1990 were designed and specified to pass that test and so additional 110 tests seldom generate actionable information. I am curious if other CHAS members have other experiences with this test?

Thanks for any information about these questions.

- Ralph

Ralph Stuart, CIH, CCHO
Environmental Safety Manager
Keene State College
603 358-2859


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