Standard air distribution ducting system used in mechanical ventilation system with heat recovery are rigid spiral ducting and flexible ducting, but semi rigid radial duct made of plastics are gaining more and more popularity.
75mm semi-rigid duct is made of PE (high-density polyethylene - HDPE). The small diameter of the duct allows You to "hide" the ducting in screeds or suspended ceilings. Semi-rigid ducts have high mechanical resistance and air tightness. What is more, the external corrugation (corrugation) of the tube assures great flexibility, which makes the assembly so much easier. The inner side of the duct is smooth to ensure low air flow resistance.
There is a semi-rigid duct version with antibacterial coating (FLX-HDPE-A) - on the inside they are covered with an antibacterial layer. In order to differentiate a 75mm semi-rigid duct with an antibacterial layer and without it:
