The purpose of the check valves (ZZ) is to prevent the effect of back draught which occurs due to various atmospheric factors, e.g. during windy conditions or when the temperature outside the building is higher than the temperature inside.

The design of the valves ensures that the air flow is only possible in one direction - to the outside. Check valves are also used in ventilation stems where several rooms have a common ventilation duct.

The valves can be used with classic fans (except for the A-MATIC, VECCO, RING and DISK series), panel fans (except for LOOP series fan) and with SYSTEM+ bodies.

Non-return valves by AWENTA ensure that the air flows in one direction only.