Under the outlet opening and recirculation opening in the tunnel is a reservoir designed to collect condensation. This reservoir demands more attention that it is usually given in practice as it is often the cause of subsequent difficult to trace compost problems.
If the reservoir is not hanging perfectly level, the drain hole is obstructed by compost residue or the condensation tube is not connected properly, then the condensation fluid will not drain away through the tube, but seeps onto the compost below. During pasteurisation this can lead to a damp patch of compost that is difficult to rid of ammonia and creates problems during mycelium growth. If the reservoir overflows while mycelium is developing, then a damp patch of incubated compost can be the trigger of mummy in the growing rooms.
Spawn pellets left behind in the reservoir also form a source of Trichoderma infection as all the recirculated air passing over the reservoir is blown directly through the compost layer.
To prevent this make a construction using a plastic flap or perforated sheet to shield the reservoir and prevent any compost or spawn falling into it during filling. Always check if the condensation reservoir is clean and working properly after filling and when cleaning the growing rooms.
Con Hermans, AdVisie ‘The mushroom cultivation advisors’