The Secretary of State must assess the levels of ozone in ambient air in all zones.

The Secretary of State must ensure that fixed measurements are taken in any zone where the concentrations of ozone have exceeded the long-term objectives specified in Schedule 4 during any of the five years preceding those measurements.

Save as provided in paragraph (4), for the purposes of paragraph (2), measurements must be taken in accordance with the reference measurement methods specified in point 8 of Section A of Annex VI to Directive 2008/50/EC.

Alternative methods to those referred to in paragraph (3) may be used provided the conditions set out in Section B of that Annex are complied with.