reg 4 NOTES TO PARTS A AND B
The addition of hazardous substances to determine the controlled quantity shall be carried out according to the following rule: if the sum (where the quantity of hazardous substance x (or category of substance) present, Q = the relevant controlled quantity (Q) from Part A or Part B, except for those substances for which column 3 of Part A contains a quantity Q*, in which case the quantity Q* shall be used in place of the controlled quantity Q in column 2) then the controlled quantity of each of the substances which are added together in accordance with each of paragraphs 5(a) to (c) below shall be deemed to be present for the purposes of sections 4(2), 14(2)(c), 23(2)(a), and of section 11(5) (as applied by the Planning (Control of Major-Accident Hazards) Regulations 1999) of the Act and of section 181 (enforcement notice to have effect against subsequent development) of the principal Act as substituted by paragraph 8 of Schedule 4.