Infectious disease aerosol exposures with and without surge control ventilation system modifications

To help better understand the transport of airborne infectious disease organisms in hospital environments when surge control strategies are implemented, tests were conducted in a recently decommissioned hospital during a one-week period. In this paper the authors evaluate the aerosol data to determine the transport of the releases of a simulated infectious aerosol in a standard patient room into the adjacent hallway under two ventilation conditions: unmodified (normal) and modified (whole floor negative air pressure) ventilation operation mode. The average hallway protection efficiencies remained relatively high (> 98%) when the ventilation system was modified for whole floor negative pressure. During four door entry/exits the average minimum hallway protection efficiencies were lower during the modified ventilation operation (i.e. 93-94%) than those for the unmodified operation (i.e. 98-99%). We note that these lower hallway protection efficiencies may be explained by the 52% reduction in the outdoor air ventilation being supplied to the hallway during the modified operation mode.