What is PM2.5? In fact, it has an easy-to-understand Chinese name called fine particulate matter, which has an important impact on air quality and visibility. PM2.5 refers to particulate pollutants with a diameter less than or equal to 2.5 microns, which is only one-twentieth the thickness of a human hair. It can directly enter the human alveoli, enter the capillaries through the alveolar wall, and then enter the entire blood circulation system. PM2.5 carries a large amount of bacteria and viruses, which can cause great harm to the human body.

A famous American medical journal once investigated and studied the relationship between PM2.5 and mortality. In one of the papers, it stated: “When the concentration of PM2.5 in the air is higher than 10 micrograms per cubic meter for a long time, the risk of death begins to rise. For every 10 micrograms per cubic meter increase in concentration, the total risk of death increases by 4%, the risk of death from cardiopulmonary diseases increases by 6%, and the risk of death from lung cancer increases by 8%.” This prospective study conducted in the United States began in 1982 and recruited 1.2 million participants. The conclusion of the paper is based on 16 years of follow-up data and is currently the most reliable evidence regarding the increased risk of death from PM2.5 pollution.

Based on the above reasons, people are alarmed by haze, because the main component of smog is PM2.5. During the heavy smog period last year, the PM2.5 index in Shijiazhuang, Shandong, and other places even exceeded 1,000. According to the PM2.5 concentration limits released by the Ministry of Environmental Protection of China and implemented on January 1, 2016, air quality can only reach the "good" standard if the annual average concentration limit is greater than or equal to 35μg/m3 and the 24-hour average concentration limit is less than or equal to 75μg/m3. This concentration limit was developed in accordance with the loosest transitional period standard recommended by the World Health Organization. In heavy smoggy weather, the measured values far exceed the standard limit by more than ten times, and the impact of smoggy weather on human health can be imagined. For the overall environment, we are unable to change it in a short time, but for small environments such as homes and offices, we can improve them by using negative ion air purifiers targeting PM2.5, which can effectively clear indoor PM2.5 and make the living environment more comfortable and healthy.

To combat and purify indoor PM2.5, most of what is used on the market currently are air purifiers, and the largest component required by air purifiers is the use of PM2.5 sensors, dust sensors, and smoke sensors.