As the source for carbon filter, you can use a single channel filter, and the filter material can be activated carbon brand AR – V. you also need two ordinary kitchen sieve with a mesh of metal with diameters of 175 and 180 millimeters. One insert to another with a small gap.
Pour activated carbon into one sieve, while the other sieve insert on top, so that the coal within was motionless. For sealing the gap of ideal rubber ring from the duct heater.
Move the whole structure into the housing channel of the filter, closer to the outlet.
Cut a strip from a foam backing and use it to seal the gap between the filter housing and the edge of the sieve. The inside of the filter insert into the gaps on the four sides of the pieces are very dense parallon, it is necessary to fix and clamp all made by you design.
The whole construction is quite simple.