Systems of ventilation
The main component of any forced mechanical ventilation is the fan. Its role according to the name is quite clear.
In front of the fan the backpressure valve (the air valve) and the filter surely is installed. The backpressure valve (the air valve) represents mechanical the device which does not allow external air to snare air ducts at idle ventilation.
The filter carries out purification of fresh air, detains on itself dust, small insects, pollen of plants. Demands periodically cleaning, do not forget about it.