PCT No. PCT/NL97/00329 Sec. 371 Date Dec. 8, 1998 Sec. 102(e) Date Dec. 8, 1998 PCT Filed Jun. 10, 1997 PCT Pub. No. WO97/47929 PCT Pub. Date Dec. 18, 1997A ventilation system, for example in the agricultural field. The ventilation system includes a ventilator and a processor module. Connections are included for connecting sensors associated with the ventilator to the processor module and on to a central processing unit. The sensors measure process quantities, such as the rotational speed, the temperature and the displaced air volume. The processor module is arranged in such a manner that in case of failure of the central processing unit and/or of the communication link between the processor module and the central processing unit, the processor module will control the ventilator on the basis of the process quantities measured by the sensors associated with the ventilator.