Part1 reported the results obtained by the field investigations about the actual status of microbial contamination and the humidity characteristics related to the microbial growth, in each part inside of an air conditioning system. About microbial growth environment, the relative humidity characteristics of both the inside of an air conditioner and air outlet were compared, and the influence of the relative humidity characteristic to microbial growth was studied. It was suggested that growth of a microbe can be suppressed by controlling the humidity environment in an air-conditioning system immediately after stopping air-conditioner operation. This paper describes the laboratory study about the influence on the microbial growth speed by controlling relative humidity. Microbial growth speed, the value of hyphal length divided by time, was evaluated using Eurottum herbartorum in this study. It was proved that the method of controlling humidity environment can suppress the microbial growth speed.
