At Cornell Ithaca, we recommend either 6 or 8 ach for labs in general, with the choice between those rates based on a visit to the qualified person named in our Laboratory Ventilation Management Plan (see our newly published JCHAS article on this topic). However, in real life, our instructional general and organic chem labs have so many fume hoods that when the hood are on, the ach in those labs is around 40 ACH. It is in bioscience labs with fewer hoods/square foot of lab where our review can make a 25% difference in lowering the ACH.

Let me know if you have any questions about this.

- Ralph

Ralph Stuart CIH

Chemical Hygiene Officer

Department of Environmental Health and Safety

Cornell University

rstuart**At_Symbol_Here**cornell.edu