Air positive and negative ions can be divided into large, medium and small ions according to their mobility. What is beneficial to the human body are small ions, also called light ions, which have good biological activity. Only small ions or small ion clusters can enter the organism.
The moving speed of ions under the action of an electric field of unit strength (V/m) is called ion mobility, which is an important parameter to distinguish the diameter of the measured ion. The smaller the diameter of air ions, the faster their migration speed. Ion mobility is an important parameter to express the size of the measured ion. The ion movement speed is inversely proportional to the ion diameter, and the ion mobility is directly proportional to the ion movement speed, so the ion mobility is negatively proportional to the ion diameter.
Air positive and negative ions can be divided into large, medium and small ions according to their mobility. Ion mobility greater than 0.4c㎡/(V`s) is a small ion, less than 0.04/(V`s) is a large ion, and between the two is a medium ion. Charged atomic groups or molecular groups that are close to the molecular size are all small air ions. These small air ions have a high speed of movement, collide with each other in the atmosphere, and continue to gather to form large or medium ions.