From: "Stuart, Ralph" <Ralph.Stuart**At_Symbol_Here**KEENE.EDU>
Subject: Re: [DCHAS-L] Lab Ventilation
Date: Tue, 23 Feb 2021 19:42:14 +0000
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Message-ID: B4AC7E35-629A-47D2-B391-F9DF9965382F**At_Symbol_Here**

> Regardless of what you are doing, you should accommodate existing lab practices based upon what ACH lab is operating at because you cannot easily adjust ACH without domino-like repercussions.

Despite the prudence of this engineering recommendation, I have very seldom seen it followed in the academic environment. In my experience, space assignments are made for administrative reasons rather than ventilation capabilities of specific spaces.

>Maximum sash opening, storage of flammables, policing lab door openings ,etc, etc is best way to maximize containment for more dangerous chemicals using whatever ACH you have. 6 ACH is very low and should never be used, although many education labsare now sized this way to ‰??save energy‰??.
I‰??m not sure what ‰??very low‰?? means in this context. Based on a review of the chemistry being used in about 80% of the spaces I visited on a research campus, 6 ACH is appropriate, as long as the system is true lab exhaust in the sense that it is not recirculated into occupied spaces. This is not always the case in buildings which have been repurposed several times. The criteria I used to make these determinations is described at Identifying General Laboratory Ventilation Requirements Using A Control Banding Strategy by Ellen Sweet and Ralph Stuart at

>For new labs, one should always devise a system assuming usages may change. I personally believe minimum 10 ACH is better, but you may have trouble establishing this for new labs.
The data reported in Laboratory Air Quality And Room Ventilation Rates: An Update by Robert C. Klein, Cathleen King, and Anthony Kosior at suggests that there is marginal value added by going as high as 10 ACH.

> >Follow up ‰?? what criteria do you use to classify high risk vs low risk research labs?

See above.
> > ‰?¢ Has anyone done Computational Fluid Dynamic (CFD) analysis of their typical labs to validate that the air flow rates and directions are sufficient?

I have seen CFD models that address these concerns. They can be helpful before lab workers move into the spaces in assessing air movement patterns, but the human element often confuses the CFD model results.

- Ralph

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


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