A system and method to adjust a pressure in a volume in a negative pressure shaft system. The method includes: a) determining pressure values that constitute a measurement for the pressure in the volume at different points in time, and storing the pressure values that have been determined, b) determining a maximum value and a minimum value from the stored pressure values, c) determining a difference value from the maximum value and the minimum value, d) comparing said difference value with a predetermined first limit value, and e) activating a pump in order to aspirate a fluid from the volume if said difference value is greater than the predetermined first limit value.
