The Challenge of Assigning General Ventilation Rates in Labs

In a previous article, we described how we used two ANSI standards (Z10 and Z9.5) to develop an institutional Laboratory Ventilation Management Program (LVMP). This paper describes our use of a control banding strategy as a key tool in this LVMP to establish target ventilation rates for specific laboratory spaces. In spaces where chemicals are used consistent with OSHA’s definition of laboratories, Cornell University in Ithaca, NY uses a default rate of 8 air changes per hour (ACH) when the lab is occupied and 4 ACH when the lab is unoccupied. The primary alternative control band for laboratory ventilation, when conditions allow, is 6 ACH (occupied) and 3 ACH (unoccupied). These ranges are used when three operating conditions are met: volatile chemical sources are controlled by local ventilation; the ventilation effectiveness within the laboratory prevents accumulation of significant concentrations of chemical vapors; and laboratory housekeeping is adequate to avoid ongoing sources of fugitive emissions in the laboratory. In this process, we also identify laboratory chemical uses that lie outside these control bands; these require specialized review to determine appropriate ventilation rates.