Almost all of the "+" natural ions are obtained from radioactivity. About 40% of the natural ions come from radioactive minerals in the ground. Each time a radioactive atom decays, highlighting the alpha particles in air, formed from 50000 to 500 000 pairs of ions. Another 40% come from radon (Rn) of air (which produces about 250,000 ion pairs for each atom of radon), and 20% comes from cosmic rays (high-energy photons from distant supernova stars). Inside premises ions "live" on average, about 30 seconds. before you get to the surface or go into the land. Outdoors ions "live" is usually a few minutes. Negative ions come from radioactivity and from the evaporation of water.
Just lightning storms and forest fires also produce ions, but since these ions are not produced during good weather, there is usually only radioactivity and evaporating water produces ions in the open air. The normal concentration in the clear weather negative ions is from 200 to 800 cm3, and positive from 250 to 1500 positive ions per cm3. Concentration indoors is usually less. Within a few hours before the storm concentration "+" ion increases tremendously, and sometimes exceeds 5000 ions/cm3. During a thunderstorm, the number of "-" ions increases up to several thousand per cm3, and the number of "+" ion often falls to 500. Ions are usually produced by high-energy processes, such as open flame or very hot object (not hot enough to ignite).
Hot objects usually emit equal numbers "+" and "-" ions. Moreover, the high dc voltage (over 1000 volts), especially when it supplied to sharp metal blades or needles, produces ions of the same polarity as the source of the input voltage. This is the basis of ion generators. The evaporating water will produce a "-" ions in the air and, as consequence, leaves the "+" ions in water that has evaporated. If the surplus remaining "+" charge does not go back into the ground, the water becomes sufficiently positive to production "-" ions stopped. For example, a fountain, a which has a motor, which sends a jet into the wall, will consistently produce "-" ions (as long as the water flows), but the fountain, running on battery power, will no longer produce "-" ions, a few minutes if the fountain is well insulated from the ground. The same is true for running on battery power ionizer. In general, for each 3×10-13 molecules of water that evaporates, one molecule of water is unnecessary "-" charge.