are major indoor and outdoor air pollutants. They are often divided into the separate categories of methane (CH₄) and non-methane (NMVOCs). Methane and other hydrocarbon VOCs are significant greenhouse gases via their role in creating ozone and prolonging the life of methane in the atmosphere. Within the NMVOCs, the aromatic compounds benzene, toluene and xylene are a hazard to health. Some VOCs also react with nitrogen oxides in the air in the presence of sunlight to form ozone, posing a health threat in the lower atmosphere by causing respiratory problems.

are major indoor and outdoor air pollutants. They are often divided into the separate categories of methane (CH₄) and non-methane (NMVOCs). Methane and other hydrocarbon VOCs are significant greenhouse gases via their role in creating ozone and prolonging the life of methane in the atmosphere. Within the NMVOCs, the aromatic compounds benzene, toluene and xylene are a hazard to health. Some VOCs also react with nitrogen oxides in the air in the presence of sunlight to form ozone, posing a health threat in the lower atmosphere by causing respiratory problems.