Adjusting CO₂ limits

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 e.g.. 2000 ppm with a moisture content of e.g. 10.5 g/kg, will give the same oxygen concentration as a maximum CO₂ limit of 1674 ppm with a moisture content of 11.5 g/kg etc.

Jan Gielen, Specialist climate & energy,
Cpoint