Instructions for filter change (see pic.):

1. Pull carefully out the vent from the wall and remove the dirty filter.

2. Grab the filter by the seams and turn it like a sock half way over the threads on the vent. 

3. Pull the filter carefully over the black filter ring. The exceeding part of the sock can be stuffed into the filter's framework.

4. The vent is now ready to be put back in place