Airborne transfer of contaminants in ventilated spaces

To assess the effectiveness of directional air flow and the influence of a disturbance such as opening and closing doors on the airborne transfer of contamination, the concentration of a tracer gas (ethane) was measured at various locations in a model consisting of four adjacent rooms between two corridors. Each room had two doors opening into the corridor. Ethane concentrations were measured as a function of pressure drop (0, +/- 0.005, +/- 0.01, and +/- 0.02 in. H2O) and time of door opening and closing (3, 6, and 9 sec). A hydrocarbon analyzer was used to measure the concentration of ethane. Contamination was transferred in the direction of decreasing static pressure and was proportional to the magnitude of the pressure differential. Opening and closing a door led to exchange of air between the spaces separated by the door regardless of the sign of the pressure differential that existed when the door was closed. The extent to which a space was contaminated by opening and closing a door was directly proportional to the time the door was open. Contaminant concentration differences between adjacent spaces were greatest when the connecting door was kept closed and the pressure differential was least. The findings indicate that modification of current practices may lead to improved protection of personnel, animals, and experiments from contamination.