Planning Circular 3/2015: Planning controls for hazardous substances

Guidance on the planning procedures around hazardous substances consent, relevant applications for planning permission and planning policies.

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Annex B


Requirement for Consent

B1. The hazardous substances consent controls are designed to regulate the presence of hazardous substances so that they cannot be present at or above controlled quantities without consent or unless an exemption to the need for consent applies.

B2. They complement, but do not override or duplicate, the requirements of the Health and Safety at Work Act 1974 ( the HSWA) or regulations made under that Act, which are enforced by HSE . Even after all reasonably practicable measures have been taken to ensure compliance with the requirements of the HSWA , there can remain a residual risk of an accident which cannot entirely be eliminated. The hazardous substances consent controls (and related requirements regarding planning permission) ensure that this residual risk to persons in the surrounding area and to the environment is properly addressed by the land use planning system.

B3. Requirements for hazardous substances consent also allow planning authorities to control the presence of such substances in light of potential future developments as indicated in the development plans for their areas.

Hazardous Substances Consent and Controlled Quantities

B4. Hazardous substances consent is required for the presence of a hazardous substance on, over or under land (which includes presence in buildings and on structures) unless the aggregate quantity of the substance present is less than the controlled quantity for that substance (section 2(1) and (2) of the Principal Act).

B5. The lists of categories of hazardous substance and named hazardous substances and controlled quantities for which hazardous substances consent is required are given in Schedule 1 to the 2015 Regulations. Categories of hazardous substances and named hazardous substances are listed in column 1 of Parts 1, 2 and 3 of the Schedule and the relevant controlled quantity is listed in column 2 [2] . With three exceptions, the substances and controlled quantities are taken from Annex I to the Directive. Hydrogen, natural gas (including liquefied natural gas - LNG) and liquefied petroleum gas ( LPG) in Part 2 have lower controlled quantities than specified in the Directive. This is because these substances are likely to be stored in locations across the UK where lower quantities than those specified in the Directive could have a major accident hazard potential.

B6. Where a substance named in Part 2 of Schedule 1 to the 2015 Regulations also falls into a category of hazardous substances in Part 1 of that Schedule, the controlled quantity in Part 2 must be used. For example, chlorine is a named substance in Part 2 with a controlled quantity of 10 tonnes. It also falls within the H2 Acute Toxic and E1 Hazardous to the Aquatic Environment categories of substances within Part 1 of Schedule 1 which have controlled quantities of 50 and 100 tonnes, respectively. In such cases, the controlled quantity of this substance will always be the controlled quantity listed in Part 2 of the Schedule, 10 tonnes in the case of chlorine (See the note at the start of Schedule 1 to the 2015 Regulations).

B7. Where a substance which is not a named substance falls within more than one of the categories of substances in Part 1 of Schedule 1, the lowest controlled quantity will apply for that substance. (See Note 7 in the Notes to Parts 1 and 2 of Schedule 1).

B8. Part 3 of Schedule 1 deals with the situation in which a hazardous substance that falls within a category in Part 1 or is named in Part 2 may be present in a quantity at or above the controlled quantity during loss of control of a process (including storage activities). This is the kind of incident that gave rise to the Directive. An example of how Part 3 might apply is given below.

Example: Part 3 of Schedule 1 to the 2015 Regulations

  • Substances W, X and Y may be used in a process to produce, under normal controlled operating processes, substance Z.
  • Under such circumstances, the site operator would not need a hazardous substances consent if the substances either do not fall within Parts 1 or 2 of Schedule 1, or they do but they are not present at or above their controlled quantity.
  • However, in the event of a loss of control of the process, substances W, X and Y might react differently to produce another substance, S, which is within Parts 1 or 2 of Schedule 1, and S might be produced at a quantity at or above its controlled quantity.
  • For this reason a consent will be required for substances W, X and Y.

B9. It is not intended that consent is required for the hazardous substances generated during a loss of control of a process (including storage). The requirement is for the site operator to obtain consent for the presence of the substance(s) which are used in that process. The controlled quantity for a process substance will be the quantity whose presence, alone or in combination with other substances used in the process, might lead to a substance within a category in Part 1 or named in Part 2 of Schedule 1 being generated at a quantity equal to or greater than its controlled quantity.

B10. Part 3 of Schedule 1 relates to "where it is reasonable to foresee" that a substance may be generated through a loss of control - see Annex M and link to HSE guidance on the COMAH Regulations and "loss of control".


B11. The 2015 Regulations specify exemptions from the requirement for hazardous substances consent (See Annex C). Site operators and planning authorities should check the criteria for exemptions carefully, especially as the specific elements of certain types of exemption have changed over the years.

Aggregate Quantities

B12. Generally, a consent will be required when the aggregate quantity of a hazardous substance is present in an amount equal to or greater than its controlled quantity (see exemptions in Annex C).

B13. In determining the aggregate quantity of a category of hazardous substance or a named hazardous substance present on land (land A), account is also to be taken of the amount of the substance held on, over or under other land (land B) which is controlled by the same person and which, in all the circumstances (including in particular the purposes for which both areas of land are used) forms a single establishment [3] with land A. In other words the quantity of the hazardous substance present on land B must be included in any calculation to establish the aggregate quantity present. There is no precise limit to the distance that may exist between areas of land that may be considered to constitute a single establishment for the purposes of section 2(2)(aa) of the Principal Act. In most cases it should be clear what constitutes the establishment having regard to all the circumstances.

B14. The person in control of the land may not necessarily be the legal owner; for example, a site may be under the control of a tenant rather than the owner. Any two bodies corporate are to be treated as being one person if one is a subsidiary of the other, or both are subsidiaries of the same body corporate (section 38(3) of the Principal Act).

The Addition Rule

B15. Even where having aggregated all of a category of hazardous substance or named substance the controlled quantity has not been reached, hazardous substances consent may still be required. The Directive, and the 2015 Regulations, require categories of hazardous substance and named hazardous substances with similar properties present below their individual controlled quantities to be considered together.

B16. To establish whether a consent is required in these circumstances, hazardous substances present in amounts less than their controlled quantities will be added together according to the addition rule (see Note 5 of the Notes to Parts 1 and 2 of Schedule 1). This involves expressing quantities of hazardous substances with similar hazards present as partial fractions of the controlled quantities and adding them together. If the sum is 1 or greater, then consent is required for each of the substances which have been included in the calculation. Up to three calculations may be required for each site as the hazards are grouped in Physical, Health and Environmental hazards. Only substances with similar properties should be aggregated, so toxic substances (Health) would not be aggregated with flammable substances (Physical). One substance may be included in more than one calculation if it has multiple hazardous properties.

B17. If a substance is named in Part 2 of Schedule 1 then the quantity in column 2 of Part 2 should be used. For substances with quantities marked with an asterisk (hydrogen, natural gas (including LNG) and LPG), the controlled quantities specified in Note 5 in the Notes to Parts 1 and 2 in Schedule 1 should be used. This is because we have adopted lower controlled quantities than the Directive for the individual presence of these substances in Scotland (see paragraph B5).

B18. An example of how the addition rule applies is set out below.

Key Points: Requirements for Hazardous Substances Consent

  • Substances in Schedule 1 to the 2015 Regulations present at or above their controlled quantities require consent (subject to the exemptions in Schedule 2).
  • In considering the need for consent, all the quantities of a substance present across all the land under the control of the same person and which forms a single establishment must be added together (aggregated).
  • Schedule 1 sets out controlled quantities for named substances, generic categories of substance and for substances which it can reasonably be foreseen may cause another hazardous substance to be present as a result of a loss of control. Schedule 1 sets out which controlled quantity applies where substances may fall into more than one of these groupings.
  • Where a number of substances are present below their individual controlled quantity, consent may still be required by virtue of the addition rule.
  • The controlled quantities in the 2015 Regulations are taken from the Directive, except in relation to Hydrogen, Natural Gas (including Liquefied Natural Gas) and Liquefied Petroleum Gas - which has implications for the use of the addition rule.

Example of the Addition Rule

The following substances are present together at the example establishment:

Substance/Category Amount present Controlled quantity Fraction
Bromine 15.00 tonnes 20.00 tonnes 15/20
Chlorine 3.00 tonnes 10.00 tonnes 3/10
Ethylene oxide 2.00 tonnes 5.00 tonnes 2/5
Propylene oxide 1.00 tonnes 5.00 tonnes 1/5
H1 acute toxic 1.00 tonne 5.00 tonnes 1/5
H2 acute toxic 5.00 tonnes 50.00 tonnes 5/50
P8 oxidising liquids and solids 3.00 tonnes 50.00 tonnes 3/50

None of these substances is present in amounts equal to or greater than its individual controlled quantity. But substances that have similar hazard characteristics have to be considered together under the addition rule.

Bromine, chlorine and the acute toxic substances (H1 and H2) have similar characteristics (health hazards - Part 1, Section H) and therefore have to be added together. Expressed as fractions of their controlled quantities the sum is:

15/20 + 3/10 + 1/5 + 5/50 = 0.75 + 0.30 + 0.20 + 0.10 = 1.35.

The sum of these fractions is greater than 1, so for each of these four substances a hazardous substances consent would be required. Any consent granted by the hazardous substances authority will be in respect of the amount of the hazardous substance present.

Ethylene oxide, propylene oxide and the oxidising substance also have common characteristics (physical hazards - Part 1, Section P). They all have physical hazards. Expressed as fractions the addition is:

3/50 + 2/5 + 1/5 = 0.06 + 0.4 + 0.20 = 0.66.

Since the sum is less than 1, there is no need for a consent for any of these three substances.


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