A:Answer HEPA stands for High Efficiency Particulate Air filter. It filters very small particles out of the air, such as smoke and dust. Activated carbon filters certain organic vapors from the air such as VOCs, ammonia, and some kinds of fumes and odors. They work well together to create a clean air environment in different ways, but for allergies such as pet dander, pollen, and smoke, the HEPA is most likely to be of direct benefit to you.