Filter Patch Bags These bags come with a small mesh installed on the front to allow for air exchange. The mesh is fine enough to allow for adequate airflow and humidity control without letting contaminants pass through. These filters can range between 0.2 and 0.5 mil. The finer mesh is the least risky but also the most expensive of the filter patch bags. As long as the mesh is 0.5 mil or less, your mushrooms should be adequately protected.
