Classification of organic peroxides

With regard to the classification of organic peroxides, there appears to be a frequent lack of clarity among applicants regarding the interpretation of the CLP Guidance and/or the CLP Regulation. What often happens is that the applicant incorrectly proposes a Type G organic peroxide classification when it should be Type F. In consultation with experts from TNO, the Ctgb discussed the European agreements on the classification of organic peroxides and clarified the ambiguities. This is explained below.

Exceptional case

The following 'exceptional case' is described in Section 2.15.6 of the 'Guidance on the application of CLP criteria':

2.15.6. Relation to transport classification

Division 5.2 within Class 5 of the UN RTDG Model Regulations covers organic peroxides. A list of currently classified organic peroxides is included in the UN RTDG Model Regulations, Section This table includes organic peroxides Type B - Type F (and some formulations Type G, so-called exempted organic peroxides).

An exceptional case in this respect is a peroxyacetic acid formulation, as currently classified in the UN RTDG Model Regulations under UN 3149, with the following description: HYDROGEN PEROXIDE AND PEROXYACETIC ACID MIXTURE with acid(s), water and not more than 5 % peroxyacetic acid, STABILISED. In the classification procedure for organic peroxides, see decision logic in Section, this formulation will be assigned to organic peroxide Type G, and consequently no label elements are allocated. In view of the above, this formulation can be classified, also in accordance with CLP, as an Oxidising liquid, Category 2. See Annex VII for additional information on transport classification in relation to CLP classification.

it is unclear from this text whether applicants must use the decision tree (Figure 14 in the same Guidance) for mixtures/products that meet the 'exceptional case’ criteria, or whether they can classify these mixtures/products as type G organic peroxide without using the decision tree. The answer is that the decision tree must be used for mixtures/products that meet the exceptional case criteria. But what makes this exceptional case exceptional? That is ‘special provision’ 196, which was allocated to mixture UN 3149 (see Recommendations on the Transport of Dangerous Goods, Model Regulations, Volume I, Twentieth revised edition). From this it can be deduced that for mixtures falling under UN 3149, the last step in the decision tree can be skipped (Is a diluent with a boiling point of ˂150° C used?). This 'diluent' refers to the solvent that is present in the product. Organic peroxides for which authorisation as a biocidal product is requested almost always contain water as a solvent. This means that when you use the decision tree, you always end up with Type F classification instead of Type G. A 'diluent with a boiling point of <150° C' is simply never used. Because this last step may be skipped for mixtures falling under UN 3149, only these mixtures end up with a Type G organic peroxide classification. Please note, therefore, that even for ‘exceptional cases’ you can only reach Type G by going through the entire decision tree and submitting all the required tests.

The classification procedure and criteria for oxidising substances or mixtures is not applicable for organic peroxides as they often do not have or have only weak oxidising properties. The exceptional case is also exceptional in the sense that if the decision tree indeed results in Type G organic peroxide classification, then it may be required to classify it as a Category 2 oxidising liquid. However, the Type G organic peroxide classification cannot be automatically replaced by the oxidising liquid Category 2 classification. For this purpose, the corresponding decision tree must also be completed and the required tests must be submitted.