Answer:

VOCs are the English abbreviation of volatile organic compounds. About the definition of VOCS, from the environmental protection sense, it refers to that organic matter in the room temperature and atmospheric pressure can be volatile and harmful. The most common are benzene, toluene, xylene, styrene, trichloro ethylene, trichloromethane, methyl chloroform.

Non-methane hydro carbon (non-methane hydro carbon) short for NMHC, refers to the volatilehydrocarbons except methane. (Usually C2-C8) They have a large light reaction activity, which is a precursor of photochemical smog.

In short, VOCS contains non methane hydrocarbons; VOC is suitable for all volatile organic compounds, while the non methane hydrocarbons are often applied only to the petrochemical industry.