[labnetwork] Practices for Aging Process Gas Cylinders

[Dennis Schweiger]

Aamer,

This is an interesting topic.  Here at UofM/LNF we have cylinders that have
been on site +4.000 days, a couple at +5,000 days.  Now most of these are
inerts (Nitrgogen, CHF3, Argon, Helium, etc....) so I'm not too worried .

For the reactive/HPM materials, we've gone to great lengths to right-size
the cylinders and gas amounts (short filling smaller cylinders) so that our
replacement cadence is about 18 months.  That's what we shoot for.  We
still have some that are over that as it's almost impossible to find a
supplier that is willing to package very small amounts of HPM gas for a
University account.

I'd also be curious as to how everyone is tracking their cylinders within
their facility?

Thanks,

Dennis Schweiger
University of Michigan/LNF
Facilities

734.647.2055 Ofc


On Thu, Mar 26, 2026 at 11:55 AM Aamer Mahmood <aamer at uchicago.edu> wrote:

> Dear Colleagues,
>
> Despite a high level of user activity, we have identified several process
> gas cylinders in our facility that are 10 years old or older and still
> contain a significant amount of gas. We are evaluating whether our current
> practices remain appropriate from both a process reliability and safety
> standpoint.
>
> I would appreciate learning how your facilities approach this issue,
> specifically:
>
>    - Whether you have established age limits for gas cylinders,
>    regardless of remaining contents
>    - Any safety or process considerations that drive those limits
>    - Whether cylinder change‑outs are handled in‑house or by specialized
>    contractors
>
> Most of the gases of interest at our facility are:
>
>    - Hydrogen (H₂)
>    - Nitrous Oxide (N₂O)
>    - Ammonia (NH₃), Silane (SiH₄), SiH₄:He (5:95)
>    - Hydrogen Bromide (HBr)
>    - Methane (CH₄), Chlorine (Cl₂)
>    - Dichlorosilane (SiH₂Cl₂)
>    - Boron Trichloride (BCl3)
>    - Silicon Tetrachloride (SiCl4)
>
> Your insights or references to existing policies would be very helpful as
> we determine next steps. You may also respond directly to me (
> aamer at uchicago.edu) if you prefer.
>
> Thank you in advance for sharing your experience.
>
> Best regards,
>
>
>
> --
>
> Aamer Mahmood
>
>
>
> *Executive Director*
>
> *Pritzker Nanofabrication Facility*
>
> *William Eckhardt Research Center*
>
> *University of Chicago*
>
> *5640 S. Ellis Ave., Chicago, IL 60637*
>
>
>
> *Tel: +1 (773) 702 8903*
>
> *Web: pnf.uchicago.edu <http://pnf.uchicago.edu>*
>
>
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