Where an air quality model is used for assessment, references to descriptions of the model and information on the uncertainty shall be compiled. The uncertainty for modelling is defined as the maximum deviation of the measured and calculated concentration levels, over a full year, without taking into account the timing of the events.

Where objective estimation techniques are used, the uncertainty shall not exceed 100%.

For substances to be analysed in the PM₁₀ fraction, the sampling volume shall refer to ambient conditions.