sorry that just looks a waste of time to me, those filters u get in in hepa filters and dehumidifiers, if they are the same as in the uk contain only a tiny amount of activated carbon, yr plants odour particles will saturate that amount of carbon in no time. U'd be constantly buying filters every couple of weeks, spending loads anyway. Y not get a proper filter the refillable type, they dont cost that much, and a fuck off bag of activated carbon and refil it every 12-18 months?? Ud be able to accurately match yr fan to the filter as u'l know all the flowrates etc?