The 10 Rules of Exhaust Air Technology

1. Exhaust air needs supply air

Make sure there is a sufficient supply of fresh air. Your hood can only extract the amount of air that flows back in as supply air.

2. Supply air always from above

Since the odours that pass by the hood rise upwards for thermal reasons, the supply air should also enter the kitchen from above. The most effective place for this is near the hot plates above the upper cabinets. With this positioning, the supply air circulates the exhaust air back to the intake area of the hood and a room-wide air-circulation process can begin.

3. Non room-sealed heating appliances

National and regional building regulations impose a number of restrictions on using extractor hoods in conjunction with fuel-burning appliances connected to a chimney (e.g. coal-burning or oil-burning room heaters and gas fires) in the same room. Extractor hoods can only be used safely in combination with non-room-sealed heating appliances if it can be guaranteed that in the flat/house no carbon monoxide is extracted from the heat-producing appliance. As soon as an exhaust air system is in operation, a negative pressure is created in a closed room. The necessary pressure compensation must only be accomplished through a supply of fresh air from outside and NOT through an extraction of air from the heat-producing appliance.

Please note the additional information which you can find here.

Additionally also note the VOGT Ab- und Zuluftmauerkästen.

4. Performance losses

As a general rule of thumb, we calculate approx. minus 5% per metre of straight, smooth air duct, taking into consideration a bend. For flexible ducts, even if they are tautly laid, approx. minus 15%.

5. Correct exhaust air cross section

Avoid reductions. Extractor hoods with 125mm or 150mm outlet diameters have powerful ventilators that require correspondingly large ducts. Reductions reduce the amount of air and increase noise levels. In particular with flat pipework, pay attention to the actual circular cross section.

6. Correct duct volume

Keep the ducts as large as possible (preferably the same diameter as the outlet opening). For external motors, only use 150-mm extraction systems. Keep bends in the outlet duct to a minimum. In terms of ventilation, two 45º-bends are better than one 90º bend.

7. Extraction performance

In order to guarantee optimal operation, the BIELMEIER Hausgeräte GmbH requires the following air ducts:

• up to 300 m³/h = Ø 100 mm (System 100 ...)
• up to 650 m³/h = Ø 125 mm (System 125 ...)
• up to 900 m³/h = Ø 150 mm (System 150 ...).

This applies to the entire air duct all the way to the outside wall, including the wall penetration systems.

We explicitly reject reductions (including the wall penetration systems), and no claims can be made if such reductions are present!

The overview „Exhaust air systems and their air extraction performance“ will provide assistance in choosing the right exhaust air system.

8. Calculation example

In order to obtain good indoor air, the extractor hood should exchange the indoor air approx. 12 times per hour.

Example:
5 x 4 x 2,5 m (kitchen measurements W x D x H) = 50 m³
50 m³ (kitchen volume) x 12(times air change) = 600 m³/h

9. Filter change

Change the charcoal and grease filter on time. Metal filters should be cleaned on a regular basis (every 2 – 4 weeks). Simple cleaning – long life expectancy.

10. Much space for re-circulation

If a re-circulation operation is desired, make sure that the air speed is not too high, in order for the charcoal filter to be able to absorb odorous particles. The higher the charcoal granule content in the filter cassette, the better the degree of cleaning.