Why the air flow in the earth is variable

Circulating air or exhaust air? The advantages and disadvantages of the trigger systems

Exhaust hoods and cooktop extractors also conduct the moisture that is created during cooking out of the room with the exhaust air. This is not the case with extractor hoods with circulating air. The latter removes grease residues and odors in the same way as with exhaust air, but not the water vapor. Therefore, when operating an extractor with circulating air, it is generally important that sufficient air exchange is guaranteed - either via an open window or automatically via a controlled ventilation system. But even with a system with exhaust air, it is important that sufficient fresh air can always flow into the interior of the house, especially if there is a room air-independent or room air-dependent fireplace such as a fireplace, a gas boiler or a coal heater in the same room. Because if the fireplace and the extractor are operated at the same time, the negative pressure generated by the exhaust air extractor could cause dangerous smoke gases to enter the room. In buildings with a particularly airtight shell, this risk exists even with fireplaces that are independent of the ambient air. A window contact switch avoids this danger. It means that the extractor can only be switched on when the window is open and thus enough fresh air can flow in. The contact switch on the window is connected to the extractor motor by cable or radio. The window contact switch acts like a guard: it transmits the position of the window sash to the receiver of the exhaust air system. If the window is open, the trigger can start.