The difference between the compost temperature and the air temperature is known as activity. Activity is the main energy source of the mushroom: without activity the mushroom cannot grow. I will explain how to influence activity.
Activity is greatly affected by air circulation in the growing room. Factors which play a major role are the filling weight, the amount of supplement, perforation or non-perforation of the plastic under the compost, cultivation in wooden trays and the quality and structure of the compost. However, once growing room has been filled, you can no longer make any changes. You can, however, still influence activity with your speed of the fan.
High fan setting
The higher the fan position, the more circulation in the growing room. More circulation provides more cooling. This is beneficial when there is a lot of activity, especially during mycelium growth. If you use a higher setting you can maintain a higher air temperature, which has the advantage that there is a smaller difference between the temperatures of the compost at the outside and in the centre of the bed.
Low fan setting
If the compost temperature is almost equal to the air temperature there is little activity. Growth stagnates. The only way to stimulate growth is to operate the fan at a slow RPM, or deactivate it. The compost will warm up by itself as a result of the natural growth process.
Rule of thumb
More activity calls for a higher fan setting, for example during mycelium growth and in the first flush. Later in the cultivation process, after the second or third flush, the fan setting needs to be gradually reduced at regular intervals. This gives you more control over mushroom growth during the rest of the cultivation process.