The need for correct air circulation normally depends on the size of the kitchen, and what type of cooking is used. However, an estimated need can be calculated quite easily, simply by calculating the size of the kitchen. (Length x width x height). Remember for the dimensions of the kitchen in open kitchen-dining areas, the dimensions of the basic kitchen-area are used, together with a small addition, as a basis of calculation.
To conserve a healthy indoor environment, the air from cooking has to be cleared out and the air circulated between 5 and 10 times an hour. For instance, will the need for a kitchen with dimensions 3m x 4m x 2.5m be up to 300 m³ (3m x 4mx 2.5m x 10). An exhaust with a capacity of at least 300m³/hr would thusly secure effective ventilation of the room.

If one is used to making small, quick meals in a relatively small kitchen, one should typically choose a model with an exhaust capacity of magnitude 2-300 m³/hr.
A family of 3 or 4 members, who are used to cooking many different types of meals in a medium-sized kitchen should typically choose a model with an exhaust capacity of magnitude 3-400 m³/hr.

Large families, where many people often are gathered in a large kitchen, where the cooking is done over a longer period of time, should choose a model with an exhaust capacity of at least 400 m³/hr.

Effective diversion of cooking fumes is also dependant on the correct operation of the cooker hood.
Often, it will be appropriate to turn on the cooker hood on the lowest setting 5-10 minutes before starting to cook, after which the exhaust is increased when more fumes and vapours are starting form. When the cooking is completed, the strength of the exhaust can be reduced once more, and one can let the cooker hood run for an additional 5-10 minutes at this strength.