User Guide to Thresholds and Classification - Environmental ...

20User Guide for Thresholds and ClassificationsThe threshold criteria for substances with explosive properties, including manufactured articles containing,incorporating, or including hazardous substances with explosive properties, are defined in Schedule 1 of theHazardous Substances (Minimum Degrees of Hazard) Regulations 2001. These criteria are described below.If a substance meets any one of the following threshold criteria, it is considered explosive within the meaningof the HSNO Act.UN Model Regulations – ‗Orange Book‘ listingAny substance or manufactured article listed in the Dangerous Goods List in chapter 3.2 of the UN ModelRegulations (United Nations, 1999b), as being class 1 (denoting it as an explosive substance).Sensitiveness and explosiveness thresholdSensitiveness measures the response of an explosive substance to some accidental stimuli. A substanceis above the sensitiveness threshold if it gives a positive result to any of the three types of test in TestSeries 2 of UN Manual of Tests and Criteria (pp 471–466).i. In a type 2(a) or UN gap test (section 12.4, UN Manual of Tests and Criteria), when confined in theprescribed steel tube and subjected to detonative shock by initiating the prescribed booster charge,which is separated from the test substance by the prescribed spacer, the substance is able topropagate a detonation as shown by fragmenting the tube completely or punching a hole through theprescribed witness plate (section 12.4.1.4, UN Manual of Tests and Criteria).ii. In a type 2(b) or Koenen test (section 12.5, UN Manual of Tests and Criteria), when confined in theprescribed steel tube with a closing plate orifice of 2.0 mm or more and subjected to intense heat asprescribed, the substance is able to propagate a detonation as shown by the tube being: fragmentedinto three of more large pieces (which can still be connected by a narrow strip); or fragmented intomany mainly small pieces; or fragmented into many very small pieces and the closing device bulgedout or fragmented section 12.5.1.4, UN Manual of Tests and Criteria).iii. In a type 2(c) time/pressure test of the effect of ignition (section 12.6, UN Manual of Tests andCriteria), when confined in the prescribed steel pressure vessel and ignited by the prescribed electricfusehead, the substance is able to produce a pressure increase from 690–2,070 kPa absolutepressure or more, within 30 ms or less (section 12.6.1.4, UN Manual of Tests and Criteria).a. A substance designed to detonate, deflagrate, or produce a pyrotechnic effectAny substance expressly designed to detonate, deflagrate, or produce a pyrotechnic effect is abovethe HSNO Act threshold for the explosive property.A substance designed to detonate will, when initiated, produce a violent chemical reaction thatproceeds through the reacted material at supersonic velocity producing heat and high pressure. Theresult of the reaction is the exertion of extremely high pressures on the surrounding medium, forming apropagating shock wave of supersonic velocity; that is, the substance explodes with a sudden loudnoise.A substance designed to deflagrate will, when initiated or ignited, produce a chemical reaction thatproceeds at subsonic velocity along the surface of and/or through the reacted material, producing hotgases at high pressures; that is, the substance bursts into flames and burns away rapidly. AJanuary 2012 EPA0109