User Guide to Thresholds and Classification - Environmental ...

68User Guide for Thresholds and Classificationsthe finest particle form in which that substance is reasonably capable of being used or rendered; orwhere it is likely or known that more than 10% of the mass of the substance will crumble into a finerparticle form, then that finer form.Details of the test criteria for the test methods mentioned above follow.Test N2 (pyrophoric solids)A substance meets criterion (a) above if it is a solid in powder form and in its commercial form ignites whilefalling, or within five minutes of settling, when poured from about a 1 m height onto a non-combustiblesurface, in one or more times out of six.Test N3 (pyrophoric liquids)A substance meets criterion (b) above if it is a liquid, and if 5 mL of the liquid, when:poured into an inert container containing an inert solid powder, ignites when exposed to air for fiveminutes, in one or more times out of six; oradded to a dry filter paper at 25°C, ignition or charring occurs on the filter paper within five minutes ofaddition of the liquid, in one or more times out of three.Test N4 (self-heating substance)A substance meets criterion (c) above if a solid cube of the substance with sides 100 mm long, when heatedto 140°C, either spontaneously ignites or experiences a 60°C rise in temperature during a 24-hour period.6.4.3. Classification criteria for subclass 4.2 substances liable to spontaneous combustion,pyrophoric and self heating substances (equivalent to UN division 4.2)There are three classification categories to subclass 4.2, substances liable to spontaneous combustion andpyrophoric and self-heating substances. The criteria for inclusion in these categories are as follows.Category A (pyrophoric substances: high hazard) – classification 4.2A (equivalent to UN PG I)‗Pyrophoric substances‘, which do not meet the criteria for subclass 4.1.2, that ignite within five minuteson contact with air under the following test conditions.a. For pyrophoric solids, if, when tested in accordance with the procedure set out in Test N.2 (section33.3.1.4, UN Manual of Tests and Criteria), the substance ignites in one of the tests, the substanceis classified category A.b. For pyrophoric liquids, if, when tested in accordance with the procedure set out in Test N.3 (section33.3.1.5, UN Manual of Tests and Criteria), the liquid ignites in the first part of the test (para33.3.1.5.3.1) or ignites or chars the filter paper in the second part of the test (para 33.3.1.5.3.2), thesubstance is classified category A.Category B (self-heating substances: medium hazard) – classification 4.2B (equivalent to UN PG II)‗Self-heating substances‘, which do not meet the criteria for subclass 4.1.2, that fail to qualify as categoryA, but when tested in accordance with Test N.4 (section 33.3.1.6, UN Manual of Tests and Criteria), giveJanuary 2012 EPA0109