Long-term surveillance of air quality in medical center operating rooms

Background: Maintenance of adequate indoor air quality (IAQ) in operating rooms (ORs) is critical to the prevention of nosocomial infection in hospitalized patients. This study evaluated the characteristics of IAQ in various ORs in a medical center. Methods: Air temperature, relative humidity, carbon dioxide (CO₂), particulate matter (PM), and bacterial concentrations were monitored in the ORs, and monthly variations were noted. Results: The mean CO₂ concentrations in the ORs were lower than the suggested level (600 ppm average over 8 hours) set by Taiwan's Environmental Protection Agency. Positive relationships were found among the number of persons, temperature (Spearman's rho coefficient [r_s] = 0.19; P < .01), and CO₂ concentration (r_s = 0.34; P < .01) in the OR. Bacterial concentration was significantly associated with PM level when adjusted for OR category and the number of persons in the room. Gram-positive bacteria (eg, Bacillus spp, Micrococcus spp, Staphylococcus spp) were frequently found in the monitored ORs. Conclusion: The IAQ in the ORs varied significantly from month to month. The number of persons in the OR affected IAQ, and a decreased PM level might indicate reduced microbial contamination in the OR.