This cultivation time is relatively long when compared to the 20 to 30 days required for Flammulina velutipes and Pleurotus ostreatus. Because oxygen is in high demand during the mushroom fruiting period, the air permeability of the filters or plugs attached to the culturing bags greatly affects development of the mushroom.Insufficient ventilation due to small or clogged holes (Fig. 1) can result in poor mycelial growth, contamination and decreased mushroom production.