need the cfms of the area
they are long for a reason .....to short and the same area gets used over and over so wears out faster ....got to balance for what u want it to do (how much cfm u need to maintain your area)
they make the filters ........it is designed to be refillable so after that year of use u can dump out the old used up active carbon and replace it with fresh active carbon ......this is at a great reduction in price 12-20 every 12 -15 months for piece of mind instead of 50-80 for a whole new filter