Ozone, or trioxygen, is a gas made up of three oxygen atoms (O3). Naturally occurring in the stratosphere (upper atmosphere), ozone protects life on Earth from the Sun’s ultraviolet (UV) radiation. However, the tropospheric ozone formation occurs when nitrogen oxides (NOx), carbon monoxide (CO) and volatile organic compounds (VOCs) react in the atmosphere in the presence of sunlight, specifically the UV spectrum. NOx, CO and VOCs are known as the ozone precursors. These ozone precursors cause a negative impact on plants and animals. Although VOCs are naturally emitted by biological organisms, NOx and VOCs are emitted during combustion of farming equipment and burning of biological materials.
It is vital that the environment is not only protected from these ozone precursors but the level of ozone precursors are monitored. The United States Air Cleansing Act (1970) empowered the Environmental Protection Agency (EPA) to maintain air cleanliness and protect public health. EPA requires states in the US to identify problematic areas through comprehensive monitoring of NOx, CO and VOCs (known as Photochemical Assessment Monitoring Stations; PAMS). In the PAMS monitoring program, there are 57 specified target compounds, mainly non-methane hydrocarbons ranging from C2 to C12. This application note describes the process for monitoring these 57 ozone precursors in ambient air.