The reference method for the measurement of sulphur dioxide is that described in EN 14212:2005 ‘Ambient air quality — Standard method for the measurement of the concentration of sulphur dioxide by ultraviolet fluorescence’.

The reference method for the measurement of nitrogen dioxide and oxides of nitrogen is that described in EN 14211:2005 ‘Ambient air quality — Standard method for the measurement of the concentration of nitrogen dioxide and nitrogen monoxide by chemiluminescence’.

The reference method for the sampling of lead is that described in Section A(4) of this Annex. The reference method for the measurement of lead is that described in EN 14902:2005 ‘Standard method for measurement of Pb/Cd/As/Ni in the PM₁₀ fraction of suspended particulate matter’.

The reference method for the sampling and measurement of PM₁₀ is that described in EN 12341:1999 ‘Air Quality — Determination of the PM₁₀ fraction of suspended particulate matter — Reference method and field test procedure to demonstrate reference equivalence of measurement methods’.

The reference method for the sampling and measurement of PM_2,5 is that described in EN 14907:2005 ‘Standard gravimetric measurement method for the determination of the PM_2,5 mass fraction of suspended particulate matter’.

The reference method for the measurement of benzene is that described in EN 14662:2005, parts 1, 2 and 3 ‘Ambient air quality — Standard method for measurement of benzene concentrations’.

The reference method for the measurement of carbon monoxide is that described in EN 14626:2005 ‘Ambient air quality — Standard method for the measurement of the concentration of carbon monoxide by non-dispersive infrared spectroscopy’.

The reference method for the measurement of ozone is that described in EN 14625:2005 ‘Ambient air quality — Standard method for the measurement of the concentration of ozone by ultraviolet photometry’.

A Member State may use any other method which it can demonstrate gives results equivalent to any of the methods referred to in Section A or, in the case of particulate matter, any other method which the Member State concerned can demonstrate displays a consistent relationship to the reference method. In that event the results achieved by that method must be corrected to produce results equivalent to those that would have been achieved by using the reference method.

The Commission may require the Member States to prepare and submit a report on the demonstration of equivalence in accordance with paragraph 1.

When assessing the acceptability of the report mentioned in paragraph 2, the Commission will make reference to its guidance on the demonstration of equivalence (to be published). Where Member States have been using interim factors to approximate equivalence, the latter shall be confirmed and/or amended with reference to the Commission's guidance.

Member States should ensure that whenever appropriate, the correction is also applied retroactively to past measurement data in order to achieve better data comparability.