Benzene is a colourless or light-yellow chemical that is liquid at room temperature. It has a sweet odour and is highly flammable. Benzene is formed from both natural processes and human activities.
Natural sources of benzene include volcanoes and forest fires. Benzene is also a natural part of crude oil, gasoline, and cigarette smoke. Normal environmental concentrations of benzene are unlikely to damage animals or plants. It does have a low to moderate toxicity for aquatic organisms, but this is only likely to be apparent when high concentrations arise from significant spills.
The indoor benzene exposure is often higher than outdoor. The outdoor air usually contains a low level of benzene from tobacco smoke, gas stations, motor vehicle exhaust, and industrial emissions. The benzene in indoor air comes from products such as glues, paints, furniture wax, and detergents.
Further, fuels such as coal, wood, gas, kerosene or liquid petroleum gas (LPG) for space heating and cooking also lead to higher benzene concentration indoors.
Polyurethane is used majorly its two major applications, soft furnishings and insulation. Its thermal decomposition consists mainly of carbon monoxide, benzene, toluene, oxides of nitrogen, hydrogen cyanide, acetaldehyde, acetone, propene, carbon dioxide, alkenes and water vapor.