Which rules apply to major-hazard chemical sites in France?

Major-hazard chemical sites in France are regulated under the Seveso III Directive 2012/18/EU, applied through the regime of classified installations for environmental protection (installations classées pour la protection de l'environnement, ICPE) in book V of the Environment Code. Sites are upper tier (seuil haut) or lower tier (seuil bas) depending on the quantities of dangerous substances; they must prepare a safety study, prevent major accidents and plan emergencies, under the control of the prefect and the classified-installation inspectorate. The Labour Code adds specific duties towards contractors and worker representatives.

Short answer

• Legal basis: Seveso III transposed by Decree 2014-284 and Decree 2014-285 of 3 March 2014 (book V of the Environment Code and the ICPE nomenclature) and the ministerial order of 26 May 2014 on the prevention of major accidents; in force since June 2015.
• Tiers: upper tier and lower tier, according to the total quantity of dangerous substances on site. France had 1,299 Seveso establishments in 2025: 702 upper tier and 597 lower tier (ecology ministry, January 2026 infographic).
• Safety study (étude de dangers): identifies accident scenarios, their effects, probability and kinetics; for upper-tier sites it must be updated at least every five years. The prefect can require a critical review by an independent expert.
• Emergency plans: internal plan (plan d'opération interne, POI) by the operator and external plan (plan particulier d'intervention, PPI) by the prefect; tested and reviewed every three years.
• Land use: technological risk prevention plans (plans de prévention des risques technologiques, PPRT) around upper-tier sites, created by the law of 30 July 2003.
• Labour law: on upper-tier sites (and on nuclear sites and some mining and underground storage sites), joint prevention measures and specific training for contractors, a compulsory health and safety commission (CSSCT), and special CSE rights (L. 4521-1 and following).

How the Seveso regime works in France

Installations listed in the ICPE nomenclature are subject to a level of administrative control that depends on their activities and the quantities involved. Seveso status is then determined by the substances and quantities present; the more demanding obligations apply to upper-tier sites. The State's inspection of classified installations, mainly located in the regional environment directorates (DREAL, with equivalent services in Île-de-France and overseas), checks compliance under the authority of the prefect, and the correct application of the Seveso directive is one of its priorities.

The safety study (étude de dangers) is the keystone. It must identify the sources of risk, the possible accident scenarios, their effects on people and the environment, their probability and how fast they develop. It forms the basis for emergency plans, public information and land-use planning. The directive also requires the domino effect between neighbouring sites to be examined, with exchange of information between operators. Site monitoring committees (commissions de suivi de site, CSS) involving residents are set up around upper-tier sites.

Why France added PPRT

On 21 September 2001, the explosion of ammonium nitrate at the AZF site in Toulouse killed 31 people and injured about 2,500. The law of 30 July 2003 on the prevention of technological and natural risks followed. It reinforced the safety studies and created PPRT around upper-tier sites, which can impose expropriation or relinquishment in the most exposed zones, reinforcement work on existing homes and restrictions on future building. In June 2025, 386 PPRT were in force.

What labour law adds on Seveso and nuclear sites

The ordinary rules continue to apply: the single risk assessment document, the explosion protection document where explosive atmospheres can occur, chemical exposure control and the prevention plan for contractors.

Common mistakes

• Treating Seveso as only an environmental issue. Labour law adds training, consultation and contractor duties on the same sites.
• Letting the safety study age. For upper-tier sites it must be updated at least every five years.
• Running the emergency plan on paper only. POI and PPI must be tested and reviewed at least every three years.

Related on excodex

• Occupational safety and health in France: law, authorities and employer duties
• Seveso III major-accident prevention: tiers and duties
• Lower-tier or upper-tier Seveso establishment?
• How often must a Seveso safety report be reviewed?
• How are explosive atmospheres regulated in France?

Standards and further reading

• Directive 2012/18/EU (Seveso III); Décret n° 2014-284 and Décret n° 2014-285 du 3 mars 2014; Arrêté du 26 mai 2014 relatif à la prévention des accidents majeurs
• Loi n° 2003-699 du 30 juillet 2003 relative à la prévention des risques technologiques et naturels et à la réparation des dommages
• Code de l'environnement, articles L. 515-15 to L. 515-26 and R. 515-39 to R. 515-50 (PPRT)
• Code du travail, articles L. 4521-1 to L. 4526-1 and L. 2315-36: Code du travail numérique
• Ministry of Ecological Transition, Seveso directive and the Risks law: https://www.ecologie.gouv.fr/politiques-publiques/risques-technologiques-directive-seveso-loi-risques
• AIDA (INERIS), Seveso establishments: https://aida.ineris.fr/inspection-icpe/risques-accidentels/seveso/etablissements-seveso

This article is general occupational safety and health information prepared by the excodex editorial team. It does not replace the applicable legislation, standards, manufacturers' instructions or the assessment of a competent OSH professional or occupational physician.