A handy way to influence pinhead numbers and the amount and size of mushrooms is by using air temperature. Air temperature is very direct and can quickly be adjusted CO2-shot is more difficult to estimate but can also be used quite effectively while time combined with CO2 development often gives mixed results.
The moment to start using air temperature to influence the number of pinheads is when the first pinheads start developing. Deciding the exact time is crucial. Acting too soon can lead to a reduction in the number of pinheads meaning the damaging consequences of a dramatically reduced yield acting too late may cause too many mushroom with the related negative effect on quality. Plus high wage countries will incur additional costs directly related to the extra labour involved.
An important aspect with this control method is the compost temperature. Be aware that compost temperature can be influenced and that in general adjusting the air temperature by half a degree can already make a difference. Changes will be seen within the space of around 24 hours after which the temperature can return to the 'old' settings.
Jos Buth, C point