The balance of positive and negative ions in the air you breathe is affected by influences in the environment in much the same way you are.
What Are Negative Ions?
Ions are natural particles in the air that have either a positive or negative charge. They get this charge by either losing or gaining an electron. Negative ions are the good guys -- they are simply oxygen atoms that have gained an electron. They attach themselves to airborne particles such as dust, pollen, smoke and dander, causing them to drop from the air. Nature provides both positive and negative ions in abundance, but when it comes to feeling good, it's the negative ions that are important.
The best natural generator for negative ions is lightning, followed by ocean surf and waterfalls. Negative ions are also abundant in mountains and forests, since all plants give off some ions. In clean, natural air, you'll find very high concentrations of negative ions. If you suspect that the air you're breathing now in your air conditioned or heated office or home isn't so good, you're right.
Negative Ions can be actively produced by high voltage electricity run through metal needles (needlepoint ionization), or passively, as a by-product of when ozone is created by corona discharge or UV light. Needlepoint ionization is by far the most effective way to produce high volume negative ions. However, negative ions have a very short life (2 - 6 minutes) and die before they can circulate completely throughout a dwelling.
Also, some high-powered ion generator will produce what has been termed "black wall", a black dust that settles on surfaces, in particular around the ion generator. The Surround Ionizers have overcome the black wall problems, but negative ionizers do have other limiting factors. An oxidation technology that uses germicidal ultraviolet light produces enough negative ions to be beneficial in removing airborne particulates in a surrounding area and in helping change the ion balance in that environment, but without creating black wall.
Negative ions purify the air by magnetically attracting to pollutants until these newly-formed larger particles become too heavy to remain in the air you breathe. Negative Ionizer Air Purifiers and Oxidation Air Purifiers continually produce negative ions, so even if one of these fallen particles is kicked up into the air, it is quickly removed again. These fallen particles are typically collected by your normal cleaning activities. The most important thing, though, is that they are taken out of the air, preventing you from inhaling them into your lungs, which is how they cause problems.
Air Purifiers That Produce Negative Ions
A negative ionizer produces the most negative ions, usually in the millions, and if dust and pollen is also an issue, a negative ionizer is a good choice: