Classification and Specific Sources of Indoor Pollution Sources Indoor pollution sources can be classified according to various criteria. The following is a classification based on properties and components, along with their specific sources: Classification by Properties Non-biological Pollution Non-biological pollution primarily originates from indoor building materials, decorative materials, household chemicals, cigarette smoke, and combustion products. For example, paints, coatings, plywood, foam fillings, and plastic veneers all contain volatile organic compounds (VOCs) such as formaldehyde, benzene, toluene, ethanol, and chloroform. Microbial Pollution Microbial pollution primarily originates from household waste, air conditioners, indoor flowers, pets, carpets, and furniture, including bacteria, pathogens, and dust mites. Classification by Components Chemical Pollution Chemical pollution primarily originates from building materials, decorative materials, and household chemicals. For example, VOCs such as formaldehyde, benzene, toluene, ethanol, and chloroform, as well as sulfur dioxide, nitrogen oxides, carbon monoxide, carbon dioxide, hydrocarbons, and suspended particulate matter, are present. Physical Pollution Physical pollution primarily refers to radioactive pollution generated by indoor and outdoor foundations and building materials, indoor and outdoor noise, and magnetic radiation from indoor appliances. Specific Sources Indoor Heating or Combustion Products from the combustion of various fuels, cooking oils, and food heating during cooking, such as sulfur dioxide, nitrogen oxides, carbon monoxide, carbon dioxide, hydrocarbons, and suspended particulate matter. Indoor Activities Large amounts of metabolic waste excreted by the human body, droplets expelled during conversation, and indoor smoking. Smoking is a significant source of harmful substances, with smoke containing at least 3,800 components. Outdoor Pollutants Main pollutants include harmful gases such as sulfur dioxide, carbon dioxide, and smoke that enter indoor spaces, causing air pollution. Human Metabolism The average adult exhales approximately 22.6 liters of CO₂ per hour, along with ammonia, dimethylamine, diethylamine, diethanol, methanol, butane, butene, dibutylene, acetic acid, acetone, nitrogen oxides, CO, H₂S, and phenol. Through the above classification and introduction of specific sources, we can understand the diversity and complexity of indoor pollution sources, and thus take corresponding measures to reduce indoor pollution and protect health. https://www.renkeer.com/indoor-air-quality/