Mycelial growth of oyster mushroom is very important. Because the management of careless mycelial growth can be caused contamination and low yield of fruit body. To reduce contamination, it is necessary to maintain clean the cooling room, inoculation room and cultivation room. In generally, most farmers maintain clean cooling room and inoculation room. However It is very difficult to cleanly manage the culture room. So we set up HEPA filter in the culture room of three farms, investigated the density and type of drop microorganism before and after using HEPA filter in the cultivation room. The density of drop microorganism after using HEPA filter in cultivation room was lower than that of before using HEPA filter. The density of drop microorganism of three farms was showed same results. Also when using a HEPA filter in the cultivation room, the contamination rate was reduced.

• Il-Sun Baek(Mushroom Research Institute, Gyeonggi-Do Agricultural Research and Extension Services(GARES))
• Yun-Kyeoung Jeoung(Mushroom Research Institute, Gyeonggi-Do Agricultural Research and Extension Services(GARES))
• Jeong-Hyun Chi(Mushroom Research Institute, Gyeonggi-Do Agricultural Research and Extension Services(GARES))