John
Air purifiers are actually fairly simple machines. Take a look at the diagram here This is a basic diagram of a generic air purifier. Keep in mind that the term air purifier is used in a number of ways and for different purposes. There is a list of the common types here to get you started There is also an exploded view of the Sun Pure SP-20C (which is the same unit as the Continental Fan CX1000 air purifier) here This is the best air purifier on the market and is used in hospitals and labs for its efficiency and effectiveness. One property of air that is usually overlooked is the noise. Air moving makes noise, so large volumes of air moving make a lot of noise. When you are outside, this is called wind. Most complaints are about the noise from portable air purifiers, but most people don't want a large piece of furniture in their room to clean the air. Shrinking the size of the unit means more air has to pass through a smaller area, that means more noise. Also, keep in mind the ability of the filter media to hold the dust it is capturing. You have to keep the air slow enough to give the filter a chance to catch the dust. If you throw a tennis ball through a chain link fence hard enough and fast enough, it will pass right through. You get the idea. I hope this helps.