Air negative ions, also called negative oxygen ions, are formed by the combination of oxygen molecules in the air and free electrons. Natural discharge (lightning), photoelectric effect, fountains and waterfalls can ionize the surrounding air and form negative oxygen ions. For example, after a thunderstorm, negative ions in the air increase and people feel very comfortable. Therefore, negative oxygen ions enjoy the reputation of "vitamin", "air vitamin", "longevity element" and "air vitamin" in the medical field. In addition, negative oxygen ions also have the main functions of sedation, analgesia, antitussive, antipruritic, diuresis, stimulating appetite and lowering blood pressure. Hongyan negative ion health paint can also release negative ions, which is a little more expensive than ordinary paint.