I've had a 4x8 Phresh carbon filter for about 6 months and finally hooked it up to an inline fan to give it a test. The filter is brand new. When the fan is pulling air from the filter I notice a slight but noticeable smell coming from it. I can't put my finger on what it smells like exactly, but it's enough that it makes my room smell like it. I know its coming from the filter itself, I detached the filter and the smell goes away. I put my hand around the flange on the filter and stuck my nose in and took a big whiff and it's definitely the filter. Is this just how carbon filters smell or is there maybe an issue with mine?