Closing the air inlet to the maximum CO₂-limit can result in a situation with an oxygen shortage The fact that this maximum CO₂-limit differs in the winter and in the summer indicates that more than one factor is influential here: It is generally well known that a too high CO₂ concentration can cause a lack of oxygen However that excessively high moisture contents (except with evaporation problems) can also lead to a lack of oxygen is not such a commonly known fact Maintaining a fixed maximum CO₂-limit in situations with a high moisture content in the growing room air creates a risk of too low oxygen concentrations which has a negative effect on the decomposition process in the compost Current climate controls do not (yet) automatically correct this But growers can adjust the maximum CO₂ limit themselves to suit the moisture content in the growing room air Calculations show that the maximum CO₂-limit must be lowered by on average 326 ppm per gram of too high moisture content and the reverse So a maximum CO₂ limit of eg 2000 ppm with a moisture content of eg 105 g/kg will give the same oxygen concentration as a maximum CO₂ limit of 1674 ppm with a moisture content of 115 g/kg etc

Jan Gielen Specialist climate & energy
Cpoint