Procedure for classifying mixtures

There is a single procedure for classifying mixtures, although it does split into two parts, one for physical hazards and another for health and environmental hazards.

  1. If you have test data available for the mixture, classify from first principles.  Test data on existing mixtures is usually found in non-CLP Safety Data Sheets, see .
  2. If you do not have test data for the mixture itself, but you have data on similar mixtures, use the bridging principles to read-across to the existing data
  3. If you can’t use the bridging principles, but do have the recipe and information on the component substances, you should gather information as follows:
    • name and identity number(s) of each component
    • recipe with %w/w of components (if a range, use maximum amount)
    • CLP classification of each component
  4. Identify any new substances which can be made by reaction in the mixture (usually carried out by a trained chemist, seek help if you do not have the right skills)
  5. Identify any extra hazards, over and above the hazards of the component substances, which might be created from the combination of substances in the mixture, e.g. self heating hazards from mixing oxidisers and flammables together (usually carried out by a trained chemist, seek help if you do not have the right skills)
  6. Make a list of all the components and all the potential hazards in the mixture

At this point, the procedure splits into physical hazards and health and environmental hazards.

Physical hazards

  1. Based on the chemistry of the substance, screen out non-relevant physical hazards (this should be carried out by a trained chemist, seek help if you do not have the right skills)
  2. If you have test data available for the relevant physical hazards, classify from first principles (or use modelling, where this is permitted)
  3. If you suspect one or more physical hazards may be present, but do not have test data, then testing will be required.
  4. The physical hazard tests are exactly the same as for substances

Health and environmental hazards

  1. You can classify the health and environmental hazards of a mixture based on the components of the mixture, even where some of the components are unknown.  You should not test a mixture on animals unless there is no alternative (although e.g. in vitro tests for corrosivity are acceptable).
  2. Use the mixture classification methods to classify, which is based on:
    • working out the overall toxicity of the mixture based on the toxicity of the components (using the LD50 data)
    • comparing the %w/w (or % v/v of a gas mixture) of each individual component to a specific threshold
    • comparing the total % w/w (or % v/v of a gas mixture) for each component with the same hazard classification to a specific threshold (an “additive” method)
    • in come cases, you can use either the individual component method, or the additive method, and may need to decide which is the most appropriate route to use

So for mixtures, you should use any published data you can get hold of for the actual mixture, or a closely related mixture; test for any unknown physical hazards; and use the mixture calculation methods for health and environmental methods.

After classifying the mixture

Once you have classified the mixture for CLP-GHS hazards, you should:


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