From: "Reinhardt, Peter" <peter.reinhardt**At_Symbol_Here**YALE.EDU>
Subject: Re: [DCHAS-L] Restaurant use of liquid nitrogen for ice cream?
Date: Fri, 31 Aug 2018 13:20:58 +0000
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU>
Message-ID: BN6PR08MB3441A18C917339E4D80B6DA3920F0**At_Symbol_Here**BN6PR08MB3441.namprd08.prod.outlook.com
In-Reply-To <72993871-90AD-40C4-8655-A6F6CA3A2229**At_Symbol_Here**keene.edu>


Yale EHS has prepared the following guidelines: https://ehs.yale.edu/sites/default/files/files/liquid-nitrogen-ice-cream.pdf

Thanks for noting "food grade" N2 again. As Ralph says below, it is cleaner and more appropriate for making ice cream. That said, it is often a special order, it must be purchased in large quantiles, and it is more expensive. We've concluded that it is nearly impossible to require "food grade" N2 for making N2 ice cream on campus.

We've also decided that it is impossible to stop people from making N2 ice cream. Lab groups and the many, many STEM programs (formal, informal, on-campus vendor) just love to make it.

Many lab dewars have gunk and particles on the bottom. Yuck. Our guidelines remind people to wash them.

Pete Reinhardt, Yale EHS

-----Original Message-----
From: ACS Division of Chemical Health and Safety [mailto:DCHAS-L**At_Symbol_Here**PRINCETON.EDU] On Behalf Of Stuart, Ralph
Sent: Friday, August 31, 2018 7:46 AM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: Re: [DCHAS-L] Restaurant use of liquid nitrogen for ice cream?

> >Would safety guidelines for liquid nitrogen use in a restaurant differ from the standards set for lab use? If so, what differences would be taken into consideration?

Yes, liquid nitrogen quality must be considered. I investigated this when a chemistry demonstration using liquid N2 to make ice cream was proposed for one of our dorms. Vendors can supply "food grade" liquid nitrogen which is produced in a way that avoids contamination from oils and other impurities in the machinery that produces the N2. This grade of liquid nitrogen is more expensive than lab N2 and the price difference led our chemists to move on to other "cool" demonstrations of chemistry in real life.

Something else I didn't know until the question arose, which is why I love this job ;).

- Ralph

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

ralph.stuart**At_Symbol_Here**keene.edu

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