Which establishments fall under Seveso III?

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Accepted Answer

An establishment falls in scope when the quantity of dangerous substances it may hold exceeds the Annex I thresholds. There are two tiers, lower and upper, and the tier decides which obligations arise. Even if no single substance passes a threshold, substances in the same hazard category are combined through the summation rule. Thresholds and two tiers Scope is set by the largest quantity that may be present — capacity, not the stock on a given day. Annex I gives two columns: lower tier and upper tier. The lower tier triggers notification, a major-accident prevention policy and public information; the upper tier adds a safety report, an internal emergency plan and an input to land-use planning. Summation rule and domino effects This is the point most often missed: no single substance has to exceed a threshold. Substances in the same hazard category are expressed as fractions and added, and if the sum exceeds one the establishment is in scope. Establishments close to one another are also treated under domino effects where an accident at one could trigger another, and information exchange between them is mandatory. Relation to Türkiye Türkiye's regulation on the prevention of major industrial accidents is the counterpart of this directive, and the Annex I thresholds are identical (measured). The same calculation engine therefore serves both regimes; what changes is the name of the documents produced and the authority they are filed with.

Obligation	Legal basis	How the page covers it
A lower-tier establishment is one where the quantities of dangerous substances equal or exceed the Column 2 thresholds in Parts 1 and 2 of Annex 1, applying the summation rule in note 4 to Annex 1.	Regulation on the Prevention of Major Industrial Accidents and Mitigation of Their Effects, art. 5(1)(b)	The Turkish regulation is the counterpart of this directive and the Annex I thresholds are identical.
The operator determines the tier of the establishment by applying the summation rule and files the notification by declaration before operations begin.	Major Industrial Accidents Regulation, art. 7(1)-(2)	Summation rule: no single substance has to exceed the threshold on its own.
The operator of a lower-tier establishment must draw up, or have drawn up, the major-accident prevention policy document taking into account the safety management system in Annex 3.	Major Industrial Accidents Regulation, art. 10(1)	At the lower tier, notification, the major-accident prevention policy and public information arise.
The operator of an upper-tier establishment must prepare, or have prepared, a safety report containing at least the information in Annex 2 and keep it at the establishment.	Major Industrial Accidents Regulation, art. 11(1)	At the upper tier the safety report is added; what changes is the name of the resulting document and the receiving authority.

Obligation	Legal basis	How the page covers it
This Directive shall apply to establishments as defined in Article 3(1).	Directive 2012/18/EU, art. 2(1)	Scope is determined by the highest quantity liable to be present at the establishment.
A lower-tier establishment is one where dangerous substances are present in quantities equal to or above Column 2 of Annex I but below Column 3; in an upper-tier establishment the quantities equal or exceed Column 3. In both cases the summation rule in note 4 to Annex I applies.	Directive 2012/18/EU, art. 3(2) and 3(3)	Threshold and two tiers: Annex I gives two columns — lower tier and upper tier.
The operator shall send a notification to the competent authority containing the information on the establishment and on the dangerous substances liable to be present.	Directive 2012/18/EU, art. 7(1)	At the lower tier, notification, the major-accident prevention policy and public information arise.
The operator shall draw up a document in writing setting out the major-accident prevention policy and ensure that it is properly implemented, and shall review and where necessary update it at least every five years.	Directive 2012/18/EU, art. 8(1) and 8(4)	The major-accident prevention policy arises at the lower tier.
The operator of an upper-tier establishment shall produce a safety report demonstrating that a safety management system is in place, that major-accident hazards and scenarios have been identified and that internal emergency plans have been drawn up.	Directive 2012/18/EU, art. 10(1)	At the upper tier a safety report, an internal emergency plan and an input to land-use planning are added.
For all upper-tier establishments the operator shall draw up an internal emergency plan for the measures to be taken inside the establishment and supply the competent authority with the information needed to draw up the external emergency plan.	Directive 2012/18/EU, art. 12(1)(a)-(b)	At the upper tier the internal emergency plan is added.
Where the risk or consequences of a major accident may be increased because of the proximity of establishments, the competent authority identifies them, and the operators concerned must exchange suitable information and cooperate in informing the public.	Directive 2012/18/EU, art. 9(1) and 9(3)	They are treated under domino effects and information sharing is mandatory.

Which establishments fall under Seveso III?

Thresholds and two tiers

Summation rule and domino effects

Relation to Türkiye

Legal basis

Türkiye — obligations and their legal basis

European Union — obligations and their legal basis

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