Air purifiers are special gadgets developed to clear away contaminating particles contained within the air we breathe. There are a lot of different types of such gadgets, and they differ in the working principium. Filter-based devices are used everywhere. Usually such gadgets are a part of HVAC system. They filter out dust from the air very effectively, but their main drawback is that they hinder the flow of air. Another type is ionizing devices. They operate by creating different charges on dust particles, causing them to pull themselves to each other and fall down. Ozone generating devices have somewhat similar way of functioning. They create oxygen rich particles that can disinfect the air. Finally, another air cleaning utility is an ultraviolet lamp, which is useful at eliminating bacteria.