On September 14, 2021, the United Nations (UN) released an electronic version of the ninth revised edition (Rev 9) of the Globally Harmonized System of Classification and Labeling of Chemicals (GHS) available free for consultation. Changes to the Eighth Revision of the GHS (Rev 8) include a comprehensive revision of Chapter 2.1 (Explosives) to better address the determination of explosion hazards when explosives are not in transit; the revision of the decision logic; the revision of the summary classification and labeling tables in Annex 1; the review and further rationalization of precautionary statements; and updated references to the Organization for Economic Co-operation and Development (OECD) testing guidelines for testing chemicals in Annexes 9 and 10. In addition, several format changes in the decision logic are noted throughout. Decision logic provides insight into the process for arriving at the appropriate classification.

The revisions to Chapter 2.1 (explosives) include the following new subchapters:

• Subchapter 2.1.1.2.2 covers substances and mixtures which are specifically excluded from the class of explosives. This includes emulsions, suspensions or gels based on ammonium nitrate which meet certain criteria; substances and mixtures which meet the criteria for classification as desensitized explosives; and substances and mixtures which have not been manufactured with a view to producing, in themselves, an explosive or pyrotechnic effect and which meet certain criteria.

• Subchapter 2.1.1.3 covers other considerations, including the relationship to classification under the UN Model Regulations; dependence on the configuration of the division; the hierarchy of categories; change of classification during the life cycle; and exclusions from the hazard class.

Table 2.1.1 on criteria for explosives now has two categories, and category 2 has three subcategories

Category	Sub-category	Criteria
1		Explosive substances, mixtures and articles which: Have not been assigned to a division and that: Are manufactured with a view to producing an explosive or pyrotechnic effect; Where Are substances or mixtures which give positive results when tested in test series 2 of the Manual of Tests and Criteria; Where The following are out of the primary packaging of the configuration to which a division has been assigned, except in the case of explosive articles assigned to a division: Without primary packaging; Where In primary packaging which does not attenuate the explosive effect, also taking into account the intermediate packaging material, spacing or critical orientation.
2	2A	Substances, mixtures and explosive articles which have been assigned: Division 1.1, 1.2, 1.3, 1.5 or 1.6; Where Division 1.4 and do not meet the criteria for subcategory 2B or 2C.
	2B	Explosive substances, mixtures and articles which have been assigned to division 1.4 and to a compatibility group other than S and which: Do not explode and disintegrate when functioning as intended; and Show no high-risk events in test 6 (a) or 6 (b) of the Manual of Tests and Criteria; and Do not require mitigation devices, other than those that may be provided by primary packaging, to mitigate a high risk event.
	2C	Explosive substances, mixtures and articles which have been assigned to compatibility group S of division 1.4 and which: Do not explode and disintegrate when functioning as intended; and Show no high-risk events in test 6 (a) or 6 (b), or in the absence of these test results, similar results in test 6 (d) of the Manual of Tests and Criteria; and Do not require mitigation devices, other than those that may be provided by primary packaging, to mitigate a high risk event.

Table 2.1.2, “Label elements for explosives”, has been revised to provide label elements based on the above categories. Subchapter 2.1.4.1, “Decision Logics”, now includes Decision Logic 2.1 (a) for explosives categories and Decision Logic 2.1 (b) for explosives subcategories. Annex 1, Summary Classification and Labeling Tables, has also been revised. The revisions include changes made to reflect revisions made to Chapter 2.1 (Explosives).

The examples below provide pictures showing some of the decision logic explanations format revisions noted throughout Rev 9.

Chapter 2.3 Aerosols and chemicals under pressure

Remark

The UN model is adopted by countries in several different ways. Some countries choose to adopt all constituent elements (classes and categories of physical, health and environmental hazards) “as is” in their legislation. The revised edition adopted will determine the details implemented within the legislative framework. Some countries adopt the criteria-based approach of the United Nations model, but exclude certain constituent elements (excluding either an entire hazard class or only certain categories within the hazard class). A criteria-based approach allows the hazards to be self-assessed, based on the criteria, to determine the classification. Other countries have chosen to adopt the basic United Nations model, but modify it to adapt it to their existing legislation or regulatory framework. This often results in a merger of regulations where the country can choose to keep existing regimes (for example., required substance classifications or classifications lists for specific substances) and self-classification elements based somewhat on UN criteria. The edition adopted by a country is often based on the most recent version available at the UN at that time. As there are currently 72 countries listed on the UN GHS website that are in the process of adopting or have adopted GHS standards, the publication of Rev 9 is expected to generate activity in these countries on how best to discuss the current version.

As indicated in our memorandum of February 16, 2021 and the Acta group (Acta^®) Global Regulatory Update for January 2021, the United States and Canada have both proposed updates to their current hazard communication regulations to align them with Rev 7 and some aspects of Rev 8. Most of trading partners are aligned or are proposing to align with Rev 7. It is expected that it will take several years before a country opts for adoption of Rev 9. Anyone proposing or attempting to characterize explosives may find the guidance and updates of Rev 9 extremely beneficial, but should consider the country in which the products are supplied before using the classification system, as it will not align with the regulatory obligations of the explosives. countries that propose or are currently aligned with Rev 7 of the United Nations GHS.