| | | A - To increase the efficiency of the hood, the length of the extraction hose and the quantity of 90° curves must be reduced to a minimum (every bend reduces the speed of the fumes and thus the extraction rate by 20%). The hose must also run straight for at least 30cm before a 90° curve. | | B - The diameter of the hole in the wall must not be smaller than the diameter of the hood hose, otherwise this narrower section will create turbulence, increased air resistance and a high noise level. | | C - The elbows must be rounded and not at a right angle because air turbulence forms near sharp edges and these are an obstacle to the complete expulsion of odours to the outside. The best solution is for bends to be rounded at 45°. | | D - It is best to use hoses that have a smooth inner surface to avoid the formation of turbulence. If runs are not straight, flexible aluminium hoses without sharp edges can be used. It is preferable not to use an extensible hose because the ridges create more resistance and noise. | | |