Environmental conditions within small-scale Agaricus bisporus mushroom production rooms

A study was conducted to demonstrate the effects of three air distribution layouts on the uniformity of temperature and humidity within Agaricus bisporus mushroom production rooms. Carbon dioxide levels were also monitored. A. bisporus mushrooms were grown in commercial-design production rooms at the Mushroom Test Demonstration Facility at the Pennsylvania State University. Three different crops were studied under three different air distribution schemes that provided a mixture of fresh and re-circulated air at an exchange rate of 6 to 9 air changes per hour. Temperature and relative humidity were measured over seven mushroom growing trays every 30 min. For the central overhead duct and drop-tube duct arrangements, the bottom production trays tended to experience the coolest, driest air conditions in the room, and the air over the middle production trays was generally warmer with higher moisture levels. The central overhead duct system, combined with two sidewall-floor ducts, produced the most spatially uniform environmental conditions of all three distribution layouts studied. Carbon dioxide levels generally remained below the 3000-ppm maximum target during the study period in all three production rooms. Improved uniformity did not correlate with an improvement in quality or increase in yield. Mushrooms grown under air temperatures less than 13 °C and at absolute humidities below 10 g m^-3 had the poorest quality.