Paragraph 18

Where an installation is authorised by a permit granted under these Regulations to carry out Part A activities, Part B activities or Part C activities which are described in Part 1 by reference to a threshold (whether in terms of capacity or otherwise), the installation shall not cease to be a Part A installation, a Part B installation or a Part C installation by virtue of the installation being operated below the relevant threshold, unless the permit ceases to have effect in accordance with these Regulations.