Development of a new technique using glass beads for dry dispersion of airborne fungal spores

To evaluate the removal of airborne microbes by air cleaners, a technique for generating airborne fungal spores in the dry state in a test chamber (dry dispersion) become necessary. The Society of Indoor Environment Japan (SIEJ) published SIEJ Standard Method No. 20110001 (SIEJ standard),in which an aerial ultrasonic oscillator was used as the device for dry dispersion. However, a more versatile apparatus is also necessary from a practical point of view. Therefore, we developed a new device using glass beads for the dispersion. Glass beads and a fungal sheet containing spores of Wallemia sebi were set in a midget impinger, which was connected to a compressor and a compact test chamber (1 m(3)). Air was blown into the impinger from the compressor. The spores on the fungal sheet were released by impingement of the glass beads when the beads were induced to float by the air blown into the impinger, and the spores were introduced to the chamber by the airflow. This newly developed technique can be used in a compact chamber system and could be applicable as an improved method for generating airborne fungal spores in the dry state in the SIEJ standard.