Samples near a frying pan, grill plate or deep fryer were taken in 10 kitchens in order to determine the composition of aerosol and vapours in the surrouding air. The main components are aerosols and low molecular aldehydes. Up to 90% of the aerosols consist of triglycerides and fatty acids. An aerosol concentration of 1.5 to 2 mg/m3 can be used as a guideline value to design the ventilation system.