User Guide to Thresholds and Classification - Environmental ...

66User Guide for Thresholds and ClassificationsUN 3242: Azodicarbonamide.Category C (low hazard) – classification 4.1.3C (equivalent to UN PG III)A substance that has one of the following UN numbers in the Dangerous Goods List, chapter 3.2 of theUN Model Regulations:UN 2956: 5-tert-Butyl-2,4,6-trinitro-m-xylene (musk xylene);UN 3241: 2-Bromo-2-nitropropane-1,2-diol; orUN 3251: Iso-Sorbide-5-mononitrate.6.3.3. DiscussionThreshold for desensitised explosivesThe HSNO Act threshold criteria for subclass 4.1.3 are equivalent to those for division 4.1(c) as set out in theUN Model Regulations, including substances previously known as substances related to self-reactivesubstances.Classification of desensitised explosivesThe HSNO Act classification categories A, B, and C for subclass 4.1.3, desensitised explosives and relatedsubstances, are equivalent to UN PGs I, II, and III, respectively, of division 4.1(c), solid desensitisedexplosives, as described in the UN Model Regulations.The UN Model Regulations assign substances to this classification by analogy with existing substances.Subclass 4.1.3 also includes substances formerly classified by the UN as ‗substances related to self-reactivesubstances‘. These substances are similar to division 4.1.2 ‗self-reactive substances‘ but have an SADTgreater than 75°C. They are liable to undergo a strongly exothermic decomposition and are liable, in certainpackaging, to meet the criteria for explosive substances in class 1.New products that are thermally stable and have, or are suspected of having, explosive properties shouldfirst be considered for class 1 using the class 1 acceptance procedure and, if necessary, the assignmentprocedure.When a substance is assigned to class 1 but is diluted to be exempted from class 1 by Test Series 6 (seeabove), this diluted substance, when meeting the classification criteria or definition for another class orsubclass, should be classified in that class or subclass at the highest concentration at which it is exemptfrom class 1. When sufficiently diluted, such substances may not meet the criteria for any class or subclass,and may be deemed non-hazardous in terms of the flammability criteria.Nature of desensitised explosivesDesensitised explosives are substances that are generally wetted with water or alcohols or are diluted withother substances to suppress their explosive properties. In their unwetted or undiluted form, they aresubstances that would meet the criteria for class 1.Explosive substances can be desensitised to different extents. For example, an explosive substance that istoo sensitive to transport can be desensitised to a degree that enables it to be transported; but in thisJanuary 2012 EPA0109