Abstract
As a method for monitoring biological cleanliness of environmental air, measurement of total airborne particles, consisting of both viable and nonviable particles, is often employed for the following reasons: (1) it is simple, easy, and does not require long incubation time or tedious procedures associated with direct viable count methods, (2) it allows real-time monitoring, and (3) it provides results that can be compared with the data in NASA standard applicable to a broad range of air cleanliness. In recent years, however, it is becoming clear that the relation between the measured concentration of microorganisms and that of total particles in the air does not always agree well with the NASA standard. In this study, we compared concentrations of microorganisms and total particles in the packaging area and the office building of a beverage plant, paying attention to particle size distribution characteristics. It was found that the size distribution of airborne microorganisms could be described by logarithmic normal distribution better than by the Junge distribution commonly used for characterizing size distributions of fine particles. Our results also suggested that, by establishing correlations between viable counts and the total particles for each specific environment, monitoring of total airborne particles would be an effective means for biological cleanliness management of environmental air.
