Difference between upper and lower tier

Seveso establishments are divided into upper-tier establishments and lower-tier establishments. This depends on the nature and the amount of dangerous substances present in the establishment.

  • Upper-tier establishments are establishments where the amount of dangerous substances is equal to or exceeds the high qualifying quantity
  • Lower-tier establishments are establishments where the amount of dangerous substances is equal to or exceeds the low qualifying quantity, but is lower than the high qualifying quantity.

There are different formulas  to calculate this qualifying quantity. 

Legal obligations

The tier of the establishment determines the legal obligations the establishment or the authorities have to meet.

Obligation Lower tier Upper tier
Draw up and implement a prevention policy for major accidents at the company X X
Draw up a notification to the authorities X X
Implement an efficient safety policy X X
Draw up a safety report   X
Draw up an internal emergency plan for the company X X
Draw up an external emergency plan (drawn up by the governor)   X
Prevention information to citizens X X