The Influence of Various Air Exchange Rates on Airborne Particles and Microorganisms in Conventionally Ventilated Operating Rooms

Abstract

Abstract Concentrations of airborne particles and microorganisms were assessed as a function of the air exchange rate in two operating theatres equipped with conventional air ventilation systems. The measurements were made with and without human activity (surgery). Under conditions without human activity the effect of the air exchange rate on viable (=microorganisms) and non-viable airborne particles was measured. Under conditions with human activity an investigation was made to determine whether the air exchange rate has a significant influence on airborne particle and bacteria concentrations. In addition, the influence of the number of persons in the operating theatres and the various operating activities were calculated. Statistical differences were found for airborne particle and airborne bacteria concentrations in supply and room air with and without human activity. From the point of view of hygiene, these differences must be considered irrelevant because of the slight margin (less than one logarithmic step) between the values. A comparison of all air exchange rates clearly shows that the number of personnel present in the operating theatre exerts the strongest influence on airborne particle concentration variance in room air. As regards airborne bacteria concentrations in room air, explanation of variance by the parameters air exchange rate, number of persons and operating activity is negligible. Summarizing the low (7.5 and 10/h) and high (15 and 20/h) air exchange rates did not increase the explanation of variance for airborne particle and bacteria concentrations although the differences were significant.