What are VOCs ?

VOCs Definition

VOCs refer to a large class of organic compounds that readily volatilize into gases at room temperature. To determine whether a substance belongs to the VOC category , its physical volatility and chemical activity are the main factors to consider.
Physical standard (boiling point/vapor pressure): This usually refers to organic compounds with a boiling point of 250°C or lower at normal temperature and pressure . For example, the WHO defines it as various organic compounds with boiling points between 50°C and 260°C.
Chemical standards (photochemical reactions): These generally refer to various organic compounds that can participate in atmospheric photochemical reactions to generate ozone or secondary organic aerosols (PM2.5 precursors).
Volatile organic compounds are generated in a wide range of ways, mainly falling into two categories: natural sources and anthropogenic sources . This article primarily focuses on VOCs generated by anthropogenic factors.

Industrial Factors

Industrial activities are major contributors to VOC emissions, primarily involving industries that use organic solvents or undergo high-temperature processing , including but not limited to the following:
1. Petrochemical industry, during crude oil refining, cracking, coking and other processes, a large amount of VOCs such as benzene series compounds and olefins are generated.
2. The evaporation of paint solvents during the spraying and baking processes in industries such as automobiles, furniture, and home appliances.
3. Printing and packaging, evaporation of organic solvents used in ink preparation, printing, and drying processes.
4. The large-scale volatilization of organic solvents such as toluene and acetone used in the reaction, separation, and purification processes of industries such as pharmaceuticals, pesticides, dyes, and coatings.
5. Material processing, during the high-temperature injection molding, foaming, and vulcanization processes of plastic and rubber products, the organic matter in the raw materials will decompose and volatilize due to heat.
6. Cleaning and degreasing, the evaporation of organic solvents (such as trichloroethylene and isopropanol) during the cleaning of parts in the electronics and machinery industries.

Traffic Factors

Vehicle exhaust, VOCs such as alkanes and olefins contained in the exhaust gases produced by the incomplete combustion of fuels such as gasoline and diesel in engines.

In Daily Life

This mainly affects indoor air quality.
1. Interior decoration, paints, coatings, adhesives, and artificial boards used in decoration may continuously release VOCs such as formaldehyde and benzene series compounds.
2. Cooking activities, kitchen fumes and gas combustion products.
3. Household chemicals, cleaners, disinfectants, cosmetics, air fresheners, insecticides, etc., which evaporate during use.

The main components and gaseous states of VOCs generated vary across different industrial fields, and the environmental and health impacts of different VOC components also differ, requiring different treatment methods and levels. We will provide our solution recommendations for specific scenarios in the next chapter.