It is absolutely illegal in every plumbing code in every state and in the European Union to place any type of valve in a roof top sewer/septic tank vent stack!
Before you buy a filter for an odor eliminator for your roof top sewer/septic tank vent stack, check them all out. Be sure the one you pick meets all plumbing and building codes.
Remember you system will not operate as it is designed with a valve in the sewer/septic tank stack. The mechanical engineers design the sewer/septic tank venting system to be a sealed system in the buildings but free open venting to the atmosphere. Beware of any system that restricts the original design in all building designs. A system with a valve that opens with the flush of a toilet and closes when operation is complete, does the same thing when you wash your hands, take a shower or bath, run the washer or dish washer, it is opening and closing continuously until it fails. And it will fail!
When it fails, if you are lucky it will fail open to the roof, and the “Rotten Egg” smell, Hydrogen Sulfide (H2) and other malodorous compounds will vent to the atmosphere, of course now you have the same problem you got rid of for a short while!
Worst than fails open, if it fails closed your plumbing system will not work until you get a ladder, climb up on the roof, remove the faulty filter, replace the filter or attempt to fix the valve on the filter.