Non-methane volatile organic compounds (NMVOCs) are a large variety of chemically different compounds, such as benzene, ethanol, formaldehyde, cyclohexane, 1,1,1-trichloroethane or acetone. Essentially, NMVOCs are identical to volatile organic compounds (VOCs), but with methane excluded. Methane is excluded in air-pollution contexts because it is not harmful. Its low reactivity and thus long livetime in the atmosphere, however, makes it an important greenhouse gas. They can cause a dense ozone close to the ground and they are a serious air pollutant and long exposure t them can cause damages to the functioning of lungs, they can damage the liver, kidneys and central nervous system. Some of them are known carcinogens.