I made one very similar to that using the exact same carbon filter material. My 3 plants were vegging and smelled a little but not too much. The filter seemed to work fine for a bit but after a week or so it lost all effectiveness. I attribute the failure to at least these factors:

--There's just not enough carbon there (main problem)
--I was sucking through it with a 6" fan and the air may have been passing through the filter material too quickly
--My plants got smellier (still vegging though) and overwhelmed the filter's abilities

IMO, the filter I made was a light duty stop-gap measure at best and a waste of resources at worst. Escaping marijuana smell should not be trifled with.

While I hastily constructed a new filter of a completely different design using granulated carbon, I made do by placing dryer sheets on the outside of the carbon blanket filter. The suction (barely) held them in place. They would work for maybe half a day before needing new dryer sheets.

$0.02