COMAH Liability

In order to work out if you will be in the scope of the COMAH 2015 Regulations, you will need to carry out an assessment based on the combination of hazardous properties (as described by CLP, or for Named Substances), and inventory.

This is very similar to the calculations required under the COMAH 2005 Regulations, except that:

  • the hazard categories are now based on CLP
  • there are more Named Substances
  • there are more hazard categories (because of the differences between CHIP and CLP).

TT Environmental Ltd have several items which can help you calculate your liability:

  • COMAH liability toolkit, see details below.
  • SevEstimateTM online calculator, which estimates your COMAH liability (without named substances, so not a full calculation), try it here.
  • SEvaluateTM calculation software, which is a desktop app (or small programme) to calculate your COMAH liability completely, details here.

We can also carry out the COMAH liability calculations for you on a consultancy basis, including linking the SEVESO calculation into your inventory, so that it updates your COMAH status automatically.

For more information or help with your COMAH liability calculation, contact Janet on 01422 24 22 22 or email Janet.

Free Download

COMAH Liability Toolkit toolkit

The COMAH liability toolkit contains 5 useful documents:
  • COMAH Factsheet
  • COMAH Calculation Factsheet
  • Top 16 COMAH calculation mistakes
  • When to notify under COMAH 2015-16
  • Should you control your inventory to avoid COMAH or stay in Lower Tier?
Free Download
Free Online Tool


Use this free web calculator to estimate your COMAH liability. It may be useful for sites wondering whether they are in COMAH, or trying to assess whether they can avoid COMAH.
Free Online Tool
Find Out More


SevaluateTM is an Excel based program which runs your COMAH (Seveso III) calculations for you, provides printable reports showing the main contributors to your COMAH liability, and allows you to predict the impact of changing your COMAH inventory on your COMAH liability.
Find Out More