The main objectives of such measurements are to analyse any trend in ozone precursors, to check the efficiency of emission reduction strategies, to check the consistency of emission inventories and to help attribute emission sources to observed pollution concentrations.
An additional aim is to support the understanding of ozone formation and precursor dispersion processes, as well as the application of photochemical models.
Measurement of ozone precursor substances shall include at least nitrogen oxides (NO and NO2), and appropriate volatile organic compounds (VOC). A list of volatile organic compounds recommended for measurement is given below:
| 1-Butene | Isoprene | Ethyl benzene | |
|---|---|---|---|
| Ethane | Trans-2-Butene | n-Hexane | m + p-Xylene |
| Ethylene | cis-2-Butene | i-Hexane | o-Xylene |
| Acetylene | 1,3-Butadiene | n-Heptane | 1,2,4-Trimethylebenzene |
| Propane | n-Pentane | n-Octane | 1,2,3-Trimethylebenzene |
| Propene | i-Pentane | i-Octane | 1,3,5-Trimethylebenzene |
| n-Butane | 1-Pentene | Benzene | Formaldehyde |
| i-Butane | 2-Pentene | Toluene | Total non-methane hydrocarbons |
Measurements shall be taken in particular in urban or suburban areas at any monitoring site set up in accordance with the requirements of this Directive and considered appropriate with regard to the monitoring objectives referred to in Section A.