Bioaerosols in health-care environments

A series of tests were conducted in an actual hospital to observe containment and removal of synthetic respiratory aerosols with respect to directional airflow and air change rate within a general patient room, an airborne infection isolation room and patient corridor. The nursing ward was comprised of a single-zone, constant air volume (CAV) distribution system. Specifically, a dedicated outdoor air system (DOAS) supplied conditioned ventilation air directly to the corridors and airborne infection isolation rooms, and, indirectly to recirculating fan coil units in each patient room. Duct traverse and flow hood measurements found that the outdoor airflow rate and exhaust airflow rate were nearly balanced in the general patient test room, producing roughly 2 ach, and, a neutral air pressure relationship with the corridor. Within both general and airborne infection isolation patient rooms, continuous aerosol production and constant volume ventilation appeared to achieve a steady-state condition. Within corridors, concentrations of greater than 5 μm aerosols decreased gradually with respect to distance, remaining above background levels to distances exceeding 80 ft in some cases. Particle size was found to influence aerosol movement in patient rooms and corridors.