VOCs are English abbreviations for organic compounds volatileorganic compounds. As for the definition of VOC, different standards have different definitions, including:
1. American ASTM D3960-98 standard defines VOC as any organic compound that can participate in atmospheric photochemistry reaction. The Federal Environmental Protection Agency (EPA) defines volatile organic compounds (VOCs) as any carbon that participates in atmospheric photochemical reactions except CO, CO2, H2CO3, metal carbides, metal carbonates and ammonium carbonate.
2. World Health Organization (WHO, 1989) defines total volatile organic compounds (TVOC) as the general term for volatile organic compounds whose melting point is below room temperature and boiling point is between 50 and 260 degrees Celsius.
3. International standards ISO 4618/1-1998 and DIN 55649-2000 define VOC as any spontaneous organic liquid and/or solid at room temperature and pressure. At the same time, the German DIN 55649-2000 standard limits the VOC
content of any organic compound whose boiling point or initial distillation point is below or equal to 250 C under normal pressure conditions.
These definitions have some similarities, but they also have their own emphases.
Formaldehyde is also a volatile organic compound, but formaldehyde is soluble in water, which is different from other volatile organic compounds. It has a wide range of indoor sources and high release concentration. Therefore, formaldehyde and other volatile organic compounds are often described separately.
Except formaldehyde, most volatile organic compounds are insoluble in water and soluble in organic solvents. The concentration of VOCs in indoor air is usually not very high, but when several VOCs coexist in indoor air, their combined effect can not be ignored. Because of their variety and low concentration of individual components, TVOC is often used to represent the total amount of volatile organic compounds in the room. TVOC is a measure of interior decoration and furniture. It is an important indicator of the degree of impact on indoor air quality.