It is important for us to know how things we use operate.  This is not only for the sole sake of knowledge, but being informed helps us make better decisions that make things better for us in the long run.  Since air purifiers can be expensive, you want your purchase to go as far as it can, just like with a car.

The basic premise of an air purifier is that it sucks in air, removes all or most of the contaminants, and then releases it back in to your home in a better state.  While that sounds simple, the actual process and the engineering of the device is more complex, yet still fairly easy to understand.

Air purifiers of the past picked up much less than what the quality ones of today do.  In addition to pollen, dust, smoke, and other allergens, modern air purifiers can take out bacteria and viruses as well.  The vast amount of contaminants removed from the air is extremely beneficial for those with breathing problems, and advantages are available for everyone, no matter what kind of health they have.

The most simple form of purification is a basic filter, which lets through air but traps particles that are bigger than a certain size.  For example, HEPA filters can trap nearly all particles down to a hundredth of a micrometer.  Virtually all dust and common allergens fit this profile, so HEPA filters work well for the majority of the population.  Also, they use less energy than other filters and release no contaminants of their own.

A more advanced filtration technique is that of ultraviolet germicidal irradiation.  With this technique, UV lights are placed discreetly inside the device, and they blast air coming past it with the rays.  These bursts of short-wavelength light sterilize the air by decomposing the microorganisms.

The type of purification usually found advertised the most is that of ionic purification (like the Ionic Breeze).  The machine generations gas ions, which attach to contaminants in the air, and these negative ions (anions) are filtered out.

There are several other types of interesting filtration methods, such as photocatalytic oxidation, which catalyzes the oxidation of bacteria through light (photo), in a similar manner to ultraviolet germicidal irradiation.  Being that there are so many different types of filters out there, you need to find which one would work best for your home, as certain methods have advantages over others.