User Guide to Thresholds and Classification - Environmental ...

85User Guide for Thresholds and Classificationsd. It is a gas that is not an organic peroxide, and that will cause or contribute to combustion at a faster ratethan air when tested in accordance with the test procedure for determining the oxidising power of gasesand gas mixtures set out in ISO 10156:1996 (ISO, 1996).In the case of criterion (b) above for oxidising solids, the physical form of the substance presented for testingshould also be considered. The substance should be tested in the finest particle form in which it isreasonably capable of being used or rendered. Where it is likely or known that more than 10% of the mass ofthe substance will crumble into a finer particle form, then the substance should be prepared and tested usingthat finer form.Where the substance is a mixture and is made up of one or more chemical elements or compounds, any oneof which meets one or more of the threshold criteria for oxidising solids or liquids given in (b) and (c) above,then the mixture will have a capacity to oxidise unless it can be shown that the exact mixture itself does notmeet any of the threshold criteria described above.7.5.2. Classification criteria for subclass 5.1.1 and 5.1.2 oxidising substances (excludingorganic peroxides)The following classification schemes apply to oxidising substances that meet any of the criteria as set out inthe Hazardous Substances (Minimum Degrees of Hazard) Regulations 2001 for oxidising substances otherthan organic peroxides. That is, substances that are organic peroxides are excluded from this classificationand are classified separately.The principal oxidising hazards arise from the ability of the substance to ignite or cause fire or combustion,usually after coming into contact with some other substance or other material. For substances with anoxidising property, classification generally follows the degree to which these effects are observed to occurwhen the substance is tested. Thus, the classification of substances with an intrinsic capacity to oxidise (thatare not organic peroxides) is based on the:ability of the substance to cause or contribute to combustion when compared with one or more referencematerials or reference mixtures; andphysical form of the substance.An oxidising substance that is in solid or liquid form is assigned one of three classification categories todenote the relative degree to which it may cause or contribute to combustion. These three categories aregenerally equivalent to the UN Packing Groups (PGs) I, II, and III. An oxidising substance that is a gas isassigned to a separate category of ‗oxidising gas‘.Technical description of the classification criteriaThe properties of a substance that will cause it to fall within a classification category for oxidising substancesare as follows.Category A (oxidising substances that are solids or liquids: high hazard) – classification 5.1.1A(equivalent to UN PG I)January 2012 EPA0109