These Regulations amend the Planning (Hazardous Substances) Regulations 2015, which list the hazardous substances and quantities of those substances which are controlled under the Planning (Hazardous Substances) Act 1990. Those Regulations also set out a process for obtaining consent for controlled substances. Classification of substances is set out in European Regulation (EC) No. 1272/2008 on classification, labelling and packaging of substances and mixtures.

Regulation 2 clarifies a rule about how controlled quantities are calculated where two or more hazardous substances are present together but individually the amounts of those substances fall below the usual controlled quantities.

The rule must be applied in relation to each of three hazard groups (categorised in Part 1 of Schedule 1 as health, physical, and environment hazards) to assess whether such substances nevertheless require consent. When applying the rule, no account is to be taken of substances present within the establishment which exceed the controlled quantity. For each hazard group, in accordance with Note 7, the lowest controlled quantity for that group should be used.