On your mid display hit the BC button and look for timmer1 & 2. If you see this just select one of the timers and then hit set. The set screen allows you to pick a start time and I think you hit set at the end. An asterick as well as a small red light will appear and the ventilation should start at the pre-selected time. This will only occur once for 20-30 mins, if you want to turn this function on in the future repeat above.