I try to avoid use of ACH as a ventilation performance criterion because the same ACH involves different volumes of air for differing floor areas and  ceiling heights.  Since these must play into the engineering design and cost, I think it best to start from the actual room size and intended use, look at supplemental exhaust that may be present (fume hoods, etc.) and use a total cfm performance requirement, especially when dealing with design considerations and engineers.

You can probably mathematically reduce this to CFM per unit volume of the room, which could be rendered as ACH, but I think it  makes criteria that are more divorced than necessary from the important parameters.

Peter Zavon, CIH
Penfield, NY

PZAVON**At_Symbol_Here**Rochester.rr.com

Dear DCHAS members:

What minimum air changes per hour (ACH) do your respective institutions require for the following laboratories while occupied?:

·         Instructional General Chemistry (no VOCs)

·         Instructional Organic Chemistry

·         Research (hazardous materials/volatiles)

Your thoughts/recommendations would be greatly appreciated.

Best,

ALFRED M. BOUZIANE | Project Manager

Environmental Health and Safety

A Department of Career and Protective Services