Hi Stephen!

 

See answers in red below:

 

1. What minimum air changes per hour (ACH) do you require for the following laboratories while occupied?

Answers below are dominated by lab exhaust in the labs, so my comments are centered on this issue. As you know, ACH numbers are generally set when lab is built. 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. 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 labs are now sized this way to “save energy”.

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.

 

Instructional/teaching lab

• High risk research lab
• Low risk research lab

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

2. Do you reduce the ACH for unoccupied laboratories? See #1. Remember thermostatic control is linked to ACH.
3. Has anyone done Computational Fluid Dynamic (CFD) analysis of their typical labs to validate that the air flow rates and directions are sufficient? EH Price has done some work on this in Canada. Before CFD, one should calculate air in vs. air out. CFD might be useful, but only if thermostatic control is stable and present.

You might wish to see following links for more specific answers:

 

https://pubs.acs.org/doi/pdf/10.1021/acs.chas.9b00013

 

https://www.pharmaceuticalonline.com/doc/common-fume-hood-containment-problems-0001

 

Best of luck on your review; I wish I could have more specific!

 

Dr. Bob Haugen

Director of Product and Technology Development

Flow Sciences, Inc.

 

910 332 4878

 

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Stephen Beaton, MSc, CHO, CRSP
Chemical Safety Manager
Environmental Health and Safety Office

DALHOUSIE UNIVERSITY
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