One manufacturer of air purifier introduced the principle of its products as follows: "After capturing electrons, air molecules will become negative ions. It is extremely beneficial to people's health and is known as the 'vitamin' in the air. Air negative ions can enhance human metabolism and improve immunity. Its concentration is particularly high in natural environments such as forests, waterfalls, lakes and oceans, so people will feel fresh and comfortable breathing in these places. Air negative ions can restore formaldehyde, cigarettes and other atmospheres Pollutants, kill bacteria, neutralize positively charged air dust, and purify the air... "Is this true?
Are there "negative ions" in nature
The original source of the term "negative ion" may be Japan. Some creative businessmen invented the concept of "negative ions" and concocted various research evidences to advocate the health effects of "negative ions". What are the facts? First, let's take a look at what can be charged in nature.
When you wear or take off clothes in a dry environment, you will be hit by static electricity. We know that solids can be charged. Rain clouds will discharge electricity to produce lightning and thunder. We know that liquid droplets can also be charged. These charged solids and liquids can indeed exist in nature for a long time.
But unlike gas molecules, they have difficulty grasping electrons. To make the gas negatively charged, it needs high temperature, strong electric field or high-energy photons to ionize the gas and release enough electrons. Some gas molecules that easily adsorb electrons, such as oxygen, water and sulfur hexafluoride, will be negatively charged in this ionized environment. But this state is unstable. Once the ionization source is removed, the density of electrons decreases, and these gases will soon lose electrons and return to an uncharged state. Therefore, "negative ion" gas molecules cannot exist stably in nature. Only thunderstorms may produce some negative ions temporarily, while forests and waterfalls have no ionization source, so there can be no high concentration of negative ions.
So, even if there are no stable "negative ion" gases in nature, we can produce them by artificially ionizing air. But are you sure this charged air is what you want?
What's the use of negative ions
The "negative ions" produced when ionizing air, that is, negatively charged oxygen molecules, can become superoxide ion free radicals with strong oxidation ability. It can be used to collect positively charged dust, react with some harmful gases, and kill pathogenic microorganisms. But it will not distinguish between normal human cells and harmful microorganisms. If you encounter cells, you'd rather kill them by mistake. Ozone is also produced in the process of ionizing air. Ozone also has strong oxidation capacity and burns the respiratory tract. It is the main pollutant in cities in summer, and its lethality is no less than PM2 5. It may burn your lungs, headache, eye pain and asthma attack.
It is also unreliable to rely on negative ions to eliminate particulate pollution. If electrons are continuously released into the air, it will charge small solid and liquid particles in the air. Charged particles are easily absorbed by door and window furniture, making them covered with a layer of ash. It is conceivable that if these particles enter the respiratory tract, they will be more easily adsorbed to the respiratory tract wall than in the uncharged state. Of course, if a positive electrode is set near the negative electrode, these negative particles can be adsorbed, but in this case, there are no negative ions in the air, which is thousands of miles away from the manufacturer's publicity.
In 2003, a consumer report of a nonprofit organization in the United States issued a report that the negative ion products used to purify the air suck. A producer of negative ion air purifier was in a hurry and took the publisher of the report, the Consumer Association, to court. The court said after investigation, the report is right, negative ion purifying air is suck. In 2005, the California District Court ruled that the company lost the lawsuit and asked the company to pay $525000 to the Consumer Association.
Therefore, "negative ions" can be sterilized and can suck dust, but it is not effective for air purification. It is far less effective than the propaganda of the manufacturers.