Most allergy approved vacuum cleaners are equipped with HEPA (High Efficiency Particulate Air) air filters that reduce the amount of airborn allergens dispersed during vacuuming. HEPA filters use activated carbon and zeolite to remove gasses, odors, chemicals, toxins and vapors. There are two basic styles, upright and canister. The upright HEPA vacuum stands on its own as a single unit, with some having an attachment hose to clean hard to reach corners. However, upright vacuums tend to leak more dusty air back into the room. HEPA canister vacuum cleaners are more effective and have a compact design that can be rolled along as you vacuum. They are more powerful because they have a separate motor.