The Planning (Hazardous Substances) (Wales) Regulations 2015

4.  The following rule governing the addition of hazardous substances, or categories of dangerous substances, applies where appropriate.

In the case of an establishment where no individual hazardous substance is present in a quantity above or equal to the relevant controlled quantity, the following rule must be applied to determine whether the establishment is covered by the relevant requirements of these Regulations. These Regulations apply to establishments if the sum is greater than or equal to 1,

• where

• q_X = the quantity of dangerous substance _X (or category of dangerous substances) falling within Part 1 or Part 2 of this Schedule; and

• Q_LX = the relevant controlled quantity for hazardous substance or category _X from Column 2 of Part 1 or from Column 2 of Part 2 of this Schedule, except as set out in the following paragraph.

• For the purposes of calculating QLX only, where the hazardous substance is one specified in column 1 of the following table, the relevant controlled quantity is as set out in column 2 of the following table A:

  Table A

  Column 1	CAS number	Column 2
  15. Hydrogen	1333-74-0	5
  18. Liquified flammable gases, Category 1 or 2 (including LPG) and natural gas (including liquid natural gas)	-	50

This rule must be used to assess the health hazards, physical hazards and environmental hazards. It must therefore be applied three times—

(a) for the addition of hazardous substances listed in Part 2 that fall within acute toxicity category 1, 2 or 3 (inhalation route) or STOT SE category 1, together with hazardous substances falling within section H, entries H1 to H3 of Part 1;

(b) for the addition of hazardous substances listed in Part 2 that are explosives, flammable gases, flammable aerosols, oxidising gases, flammable liquids, self-reactive substances and mixtures, organic peroxides, pyrophoric liquids and solids, oxidising liquids and solids, together with hazardous substances falling within section P, entries P1 to P8 of Part 1;

(c) for the addition of hazardous substances listed in Part 2 that fall within hazardous to the aquatic environment acute category 1, chronic category 1 or chronic category 2, together with hazardous substances falling within section E, entries E1 and E2 of Part 1.

The relevant provisions of these Regulations apply where any of the sums obtained by (a), (b) or (c) is greater than or equal to 1.