Designed according to the steady pressure drop method at the point from 0, 8 to 1 pa / m The rectangular cut manufactured from high quality galvanized plate according to the Pittsburgh method and the other parts connected with flanges manufactured from special galvanized profile. Among the flanges a rubber pad is used to achieve the maximum tightness. The round cut is manufactured also from galvanized plate and the unions are done with flanges or “muffes”. The connection to each machine is achieved with a flexible, chock-absorbing union with two stripes of galvanized plate, between which there is a flexible polypropylenium stripe. A layer of glass wool covered with a thin sheet of aluminum, offering mechanical protection or frelen. The hanging up of the ducts is done with galvanized sticks and galvanized supporting, while the round ones with round bases from galvanized supporting and colored plate.