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