The Control of Major Accident Hazards Regulations 2015

4.  The following rules governing the addition of dangerous substances, or categories of dangerous substances, apply where appropriate.

In the case of an establishment where no individual dangerous substance is present in a quantity above or equal to the relevant qualifying quantity, the following rule must be applied to determine whether these Regulations apply to the establishment.

An establishment is an upper tier establishment if the sum:

q₁/Q_U1 + q₂/Q_U2 + q₃/Q_U3 + q₄/Q_U4 + q₅/Q_U5 + … 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_UX = the relevant qualifying quantity of dangerous substance or category x from Column 3 of Part 1 or from Column 3 of Part 2 of this Schedule.

An establishment is a lower tier establishment if the sum:

q₁/Q_L1 + q₂/Q_L2 + q₃/Q_L3 + q₄/Q_L4 + q₅/Q_L5 + … 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 qualifying quantity for dangerous substance or category x from Column 2 of Part 1 or from Column 2 of Part 2 of this Schedule.

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

(b)for the addition of dangerous 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 dangerous substances falling within section P, entries P1 to P8 of Part 1;

(c)for the addition of dangerous 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 dangerous substances falling within section E, entries E1 and E2 of Part 1.

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