Fat sam is right, with water carbon filters there will not be as much carbon available because the water must pass through it so there must be spaces between the carbon that allows the water to freely flow through, but also the carbon must be dense enough to grab certain pollutants. When you do not use the water carbon filter for air, much more carbon is available to bond with odor particles because air is composed mostly not of molecules, but of elements, namely nitrogen (~80%) and oxygen (~20%). Nitrogen and oxygen cannot easily fit between the carbon molecules in an air filter because the carbon is very dense, but water, because it is a larger molecule, cannot pass through this tightly packed carbon. The reason that retailers offer both kinds is that water carbon filters are more economically viable because they use less carbon. They do this with simple science. Water is polar and thus attaches to elements and increases the size, thereby making it plausible that less carbon is inside the filter. The only way water carbon filters will increase efficiency of odor control is if they are used IN WATER! Any air filtration should consist of air filters due to the physical properties in them that seperate them from water filters.
