Bioaerosols from numerous sources have been implicated in respiratory diseases. This study evaluated the characteristics and weekly variations in indoor air in a medical intensive care unit (ICU) in northern Taiwan for 1 year. It also investigated the impact of patient visiting activities on the indoor climate in the medical ICU. A 4-bed room with patients in the medical ICU was selected for long-term air monitoring. Air temperature, relative humidity, CO(2), particulate matter, bacteria, and fungi were measured. Approximately 90% of the CO(2) samples exceeded 1000 ppm, and 20% of the fine particle samples exceeded 35 microg/m(3). The levels of bacteria and fungi varied during the survey period. The measured values for all indoor air characteristics except bacterial concentrations were higher after patient visitation than before patient visitation. A significant association was found between the coarse particle concentration and the number of patient visitors. Patient visiting activity impacts the indoor air quality of the ICU environment, especially in terms of coarse particle concentrations. Periodic monitoring of ventilation system efficiency is needed to ensure optimal indoor air quality.
