After the negative ions are combined with the bacteria, the bacteria produce structural changes or energy transfer, resulting in the death of the bacteria. Negative ions can also effectively remove various harmful substances in the air, such as certain harmful chemicals and volatile organic compounds VOC. Eco-grade negative ions refer to negative oxygen ions with small particle size, high activity and long natural diffusion distance. In the absence of external force, the natural diffusion distance can reach 4-5 meters.