- The attenuators should have adequate silencing capabilities and low air resistance as well as be as small as possible. With the introduction of VDI 6022, specific hygiene requirements for air condition systems. Certified for use by VDI 6022 Parts 1 and 3, Din 1946 Part 4, and VDI 3802. High protection against damage. High-temperature resistance materials. Can be installed vertical or horizontal. The bent attenuator is available.