I. A situation where harmful chemical, physical, and/or biological factors enter the indoor air and have reached a degree that directly or indirectly, in the short term or in the long term, or perhaps potentially, have a harmful impact on human health.
  People have known about infectious pathogens in indoor air for a long time, but they know less about other harmful factors. Originally, as early as when humans lived in caves and heated themselves by lighting fires, there was smoke pollution. However, at that time, the scale of such effects was very small, the duration was very short, and people's outdoor activities were very frequent, so there was no obvious harm from indoor air pollution.
  With the height development of human civilization, especially since the middle of the 20th century, due to the increase in the consumption of civilian fuels, the variety and quantity of chemical products and electrical equipment entering the indoor environment have increased, and because houses in cold regions have been built more and more tightly to save energy, indoor pollution factors have gradually increased while the ventilation and air exchange ability has weakened. This has led to the concentration of some pollutants in indoor air being several tens of times higher than that in outdoor air.
  People spend about 80% of their time indoors on average every day, and some people's indoor activity time even exceeds 93%. Therefore, the relationship between indoor air quality and human health is even closer and more important. As early as 2003, the World Cleanliness Organization released the "2002 World Cleanliness Report", which clearly listed indoor air pollution along with hypertension, high cholesterol, and obesity as one of the top ten threats to human health.
  II. Indoor Air Pollution - Damage
  American experts have found that there are over 500 volatile organic compounds in indoor air, among which there are more than 20 carcinogenic substances and over 200 pathogenic viruses. The most damaging ones include radon, formaldehyde, benzene, ammonia, esters, trichloroethylene, etc.
  A large number of shocking facts have confirmed that indoor air pollution has become a "invisible killer" that harms human health and has become a concern for all countries around the world. Research shows that the pollution level of indoor air is 2-5 times more severe than that of outdoor air, and in special cases, it can reach 100 times. Therefore, the United States has classified indoor air pollution as one of the five environmental factors that harm human health.
  The World Cleanliness Organization also lists indoor air pollution along with hypertension, high cholesterol, and obesity as one of the top ten threats to human health. According to calculations, nearly half of the world's population is exposed to indoor air pollution, and indoor environmental pollution has led to 35.7% of respiratory diseases, 22% of chronic lung diseases, and 15% of bronchitis, bronchitis, and lung cancer.
  In May 2012, according to the investigation and calculation of the Environmental Inspection Center of the China Interior Decoration Association, the number of deaths caused by indoor air pollution in China each year has reached 111,000, with an average of approximately 304 deaths per day, equivalent to the number of deaths caused by car accidents in the country every day.
  III. Indoor Air Pollution - Management Methods
  Plant elimination method
  Chlorophytum comosum, Aloe vera, and Sansevieria trifasciata can appropriately absorb indoor pollutants such as formaldehyde and improve the indoor air pollution situation; jasmine, lilac, honeysuckle, and morning glory, etc., release antibacterial substances that can kill certain bacteria in the air, inhibit the growth of tuberculosis, dysentery pathogens and typhoid bacteria, and make the indoor air clean. However, the adsorption effect of plants is relatively weak, and they are usually used as auxiliary methods.
  Activated carbon adsorption method (air purifier)
  Activated carbon can have an adsorption effect on indoor harmful gases. It is made by processing materials such as wood charcoal, bamboo charcoal, various shells and coal through a series of processes such as crushing, sieving, catalyst activation, rinsing, drying and selection.
  Enhanced ventilation method
Usually, in spring, summer and autumn, families should keep ventilation openings or frequently open "small windows"; in winter, windows should be opened for at least 10 minutes in the morning, noon and evening every day. Normally, after using chemical agents, windows should not be closed immediately; at least ventilation and air exchange should last for 30 minutes. Pay attention to keeping the air in the kitchen clean. After each cooking session, windows must be opened for ventilation; when frying or deep-frying food, ventilation should be strengthened even more. 

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