Technical Decision Trees

The technical decision trees depict a sequential logic flow to support suppliers in classifying the health hazards of hazardous products destined for Canadian workplaces in accordance with the requirements of the Hazardous Products Regulations (HPR).

The technical decision trees cover key classification requirements identified in each Subpart of Part 8 of the HPR. They are not exhaustive of all classification requirements of the HPR and may not include all relevant classification considerations for any particular hazardous product.

Two sets of technical decision trees are currently published. One set is in respect of the classification requirements of the amended HPR and the other set is in respect of the classification requirements of the former HPR. Once the 3-year transition period being provided to suppliers to transition from the former HPR to the amended HPR ends on December 14, 2025, the set in respect of the former HPR will be removed. Suppliers interested in learning more about the amendments to the HPR can also refer to the Amendments to the Hazardous Products Regulations webpage.

The technical decision trees are intended to supplement the HPR and the Guidance on the WHMIS supplier requirements (‘WHMIS Supplier Guidance’). The technical decision trees do not introduce different or additional requirements beyond those of the HPR.

Prior to using the technical decision trees, users should familiarize themselves with all classification requirements of the HPR, the amended or the former as applicable. These requirements include those of Part 2, which provides a general overview of procedures to be followed in the hazard classification process, types of data that must be considered and principles that are relevant to classification.

Users are encouraged to consult the WHMIS Supplier Guidance where additional guidance is needed. The WHMIS Supplier Guidance provides a more exhaustive overview of considerations when conducting a classification evaluation than can be provided in the technical decision trees.

When classifying the health hazards of a hazardous product, users must gather all available data. For more information on types and sources of data, consult section 2.1 of the HPR and the discussion of that section in the WHMIS Supplier Guidance for a product that is a substance or material and subsection 2.2(2) of the HPR and the discussion of that subsection in the WHMIS Supplier Guidance for a product that is a mixture.

Suppliers may apply either the set of technical decision trees related to the amended HPR or the set related to the former HPR during the 3-year transition period. Among each set, there is one technical decision tree for a product that is a substance (or material in the case of Subpart 11), and one for a product that is a mixture, for each health hazard class of Part 8 of the HPR. To determine which trees to apply, suppliers must determine whether their product is a substance/material or a mixture.

Users are referred to section 2 of the Hazardous Products Act (HPA) for definitions of the terms ‘substance’ and ‘mixture’. The term ‘material’ is not defined in the HPA, but under the HPR it is generally used in the context of Biohazardous Infectious Materials.

All available data must be evaluated against the criteria for each health hazard class, whether using the technical decision trees for a substance/material or the trees for a mixture.

Although the term ‘substance’ refers, in principle, to a single entity, users need to consider whether any impurities, stabilizing solvents or stabilizing additives are known to be present in the substance and that need to be considered for classification. For more information, consult subsection 2(6) of the HPR and the discussion of this subsection in the WHMIS Supplier Guidance.

In case of discrepancy between the technical decision trees and the HPA and the HPR, amended or former as applicable, the official versions of the HPA and the HPR prevail.

The technical decision trees may be updated periodically to correct errors, to provide clarification or to address amendments to the HPR. Users who elect to use these technical decision trees are advised to regularly refer back to this page to ensure they are applying the latest versions of the trees, whether for the amended or former HPR.