Kuuluiskohan tää juttu tänne:
http://www.trifield.com/content/about-air-ions/tässä alla vähän ja loput linkissä.
Almost all positive ("+") natural ions during fair weather come from radioactivity. About 40% of these natural air ions come from radioactive minerals in the ground. Each time a radioactive atom decays near the air, it typically ejects an energetic alpha particle, produces 50,000 - 500,000 air ion pairs as it travels a few cm through the air. Another 40% comes from radon in the air (which produces about 250,000 ion pairs for each radon atom), and 20% comes from cosmic rays (high-energy protons from distant supernovas). Indoors, ions "live" typically 30 seconds before touching a surface and shorting to ground. Outdoor ions usually "live" several minutes more. Natural negative ions usually come from radioactivity and evaporating water. Lightning, thunderstorms, and forest fires can contribute "+" and "-" ions, but these ions are not produced under everyday conditions.
Ions cannot be produced without an energy source. An "energy source" means, heat or flame, radioactivity, frictional rubbing, electricity, evaporation (which is a heat process), etc. Minerals that are not radioactive do not spontaneously emit ions. Normal fair-weather ion concentrations are 200 to 800 negative and 250 to 1500 positive ions per cubic centimeter. Indoor levels are usually lower. Several hours before a storm, + ion concentration will increase dramatically, sometimes exceeding 5000 ions per cubic centimeter (cm3). During a storm, - ions increase to several thousand while + ions decrease, often to below 500.
Ions can also be produced by high-energy events, such as an open flame or a glowing hot object. Hot objects usually emit equal numbers of + and - ions. High DC voltage (over 1000 Volts), especially when connected to pointed metal edges or needles, will produce ions of the same polarity as the voltage source. This is the basis of electric ionizers. Evaporating water will produce - ions in the air and as a consequence leave + charges behind in the water that hasn't yet evaporated. If the excess + charges left behind are not conducted back to ground, the water will become + enough that - ion production will cease. For example, a fountain that has a motor that plugs into the wall will continuously produce - ions (until the water runs out) but a battery operated fountain will stop producing - ions after a few minutes if the fountain is well insulated from ground. The same is true of a battery-powered air ionizer. In general, for about every 3x1014 water molecules that evaporate, one water molecule carries an excess - charge.