Assessing general ventilation effectiveness in the laboratory

The goal of a laboratory’s general ventilation system is to control airborne contaminants below concentrations of concern while maintaining a comfortable environment. One concern while managing general laboratory ventilation is how uniformly the room is ventilated. We have observed that, depending on the configuration of the ventilation supply and exhaust points relative to the geometry of the room, there may be areas of a laboratory that are less well-ventilated than others. This factor must be assessed when assigning minimum general ventilation rates for that lab. In order to determine how effective general ventilation systems are in existing laboratories on the Cornell campus, we have measured the concentration decay rates of carbon dioxide at a variety of locations in the room after raising the CO2 level across the room above 10,000 parts per million. This paper describes the reasons for this work, the method we use, and reports our observations about this approach to assessing laboratory ventilation effectiveness.