I should have said that air exchanges are not only not needed but are not desired during the colonization (spawn run). You want a build up of a certain amount of CO2...5,000 to 10,000 ppm for proper growth. In nature the mycelium would be below ground and there would be a build up of metabolic gasses as the mycelial net extends itself. Much of it would dissapate to the surrounding soil/nutrient mass, but in gerneral high concentrations of CO2 (>10,000 ppm) are seen. In a jar dissapation is not possible if the jar is air tight. But to loosen the top or to invert the lid insert (as is commonly done) opens a contaminant vector pathway for the introduction of contaminants.

A filter disc/patch allows for a build up of CO2 within the jar but also allows dissapation of the metabolic gasses...the old gas-pressure-temp laws of chemistry flash before my eys In effect mimicing nature by allowing for limited dissapation and a build up of CO2 around the mycelial net. Anyway this is the reason for no air exchanges and the benefit of filter discs/patches...you need a build up of CO2 during coloinzation, but you don't want the mycelium to gas itself to death in the process. Lesson here? Don't feed your shrooms beans!!!

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[This message has been edited by Shroom Mage (edited January 27, 2000).]