Aside from all the filter types and extra features that an air purifier might offer, it’s important to know which AIR FLOW TYPE is best for the room you are filtering. That’s right, air flow design type- which basically refers to the location an air purifier draws in the contaminated air and where it emits the clean, purified air. Although, there may be variations of these air flow types, most air purifiers will fall into one of three categories:
Bottom Inlet Design
Air purifiers with a bottom inlet design imply air flow that is drawn from the bottom of the unit and is pushed through the series of filters, sending gentle puffs of filtered air through the sides and top of the unit. Examples of this type include Blueair, Airgle, Allerair, IQAir and many others. In our opinion, these units function better on hardwood floors or tiled surfaces, where the surrounding air can pass easily under the unit and be drawn up through the filters. We do not recommend standing these air purifiers on heavy carpets, especially if they are old and dusty. Carpets will release lent fibers and dust on a continual basis, and will ultimately shorten the life of the HEPA filters.
Front Inlet Design
Air purifiers with a front inlet design both draw in and expel the air from the front of the unit. These types of purifiers are useful for placing against a wall or against furniture to keep it out of sight and avoid any tripping hazard. Examples of this air flow type include Alen Air, Surround Air, Alive Air and many more. Keep in mind that if you need to filter a large room, an air purifier works better if it is placed as near the center of the room as possible to permit good circulation. Since front inlet design air purifiers can only draw air from one side, they do not work well when placed in the center of the room.
360 Degree Inlet Design
The 360 degree inlet design or “drum style” can be downright ugly compared to other styles, but is, in fact, one of the most effective methods for filtering indoor air. -But be careful…we found units that look like the drum style (like the Allerair) but function as bottom-inlet filters. True examples of the 360 degree air flow design include the Airpura and the American-made Austin Air. These units draw in the surrounding air from all sides and pass through large, round, cartridge-type filters. Changing these filters can be a little cumbersome but they tend to last longer than the flat, boxy counterparts. We highly recommend the 360 degree style filtration if you need to move a lot of air- like up to 2000 square feet.
Your choice of air purifiers is determined by many factors, one of which may likely be “where” the unit will be placed. It is recommended to read a full air purifier and humidifier review prior your decision to buy one. This space may likely determine which air flow type will work best for your situation, and then you can narrow down your choices within that category.