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2.1.4.: Additional Classification Considerations

2.1.4.1. The classification of substances, mixtures and articles in the explosives hazard class and further allocation to a division is a very complex, three step procedure. Reference to Part I of the ►M4  UN RTDG ◄ , Manual of Tests and Criteria is necessary.

The first step is to ascertain whether the substance or mixture has explosive effects (Test Series 1). The second step is the acceptance procedure (Test Series 2 to 4) and the third step is the assignment to a hazard division (Test Series 5 to 7). The assessment whether a candidate for ‘ammonium nitrate emulsion or suspension or gel, intermediate for blasting explosives (ANE)’ is insensitive enough for inclusion as an oxidising liquid (section 2.13) or an oxidising solid (section 2.14) is answered by Test Series 8 tests.

Explosive substances and mixtures wetted with water or alcohols, or diluted with other substances to suppress their explosive properties, may be treated differently in terms of classification and other hazard classes may apply, according to their physical properties (see also Annex II section 1.1.).

Certain physical hazards (due to explosive properties) are altered by dilution, as is the case for desensitised explosives, by inclusion in a mixture or article, packaging or other factors.

The classification procedure is set out in the following decision logic (see Figures 2.1.1 to 2.1.4).

Figure 2.1.1
Overall scheme of the procedure for classifying a substance, mixture or article in the class of explosives (Class 1 for transport) image
►(2) M2  
►(2) M4  

Figure 2.1.2
Procedure for provisional acceptance of a substance, mixture or article in the class of explosives (Class 1 for transport) image

Figure 2.1.3
Procedure for assignment to a division in the class of explosives (Class 1 for transport) image

Figure 2.1.4

Procedure for the classification of ammonium nitrate emulsion, suspension or gel (ANE)

image

2.1.4.2. Screening procedure

Explosive properties are associated with the presence of certain chemical groups in a molecule which can react to produce very rapid increases in temperature or pressure. The screening procedure is aimed at identifying the presence of such reactive groups and the potential for rapid energy release. If the screening procedure identifies the substance or mixture to be a potential explosive, the acceptance procedure (see section 10.3 of the ►M4  UN RTDG ◄ , Manual of Tests and Criteria) has to be performed.

Note:

Neither a series 1 type (a) propagation of detonation test nor a series 2 type (a) test of sensitivity to detonative shock is required if the exothermic decomposition energy of organic materials is less than 800 J/g. For organic substances and mixtures of organic substances with a decomposition energy of 800 J/g or more, tests 1 (a) and 2 (a) need not be performed if the outcome of the ballistic mortar Mk.IIId test (F.1), or the ballistic mortar test (F.2) or the BAM Trauzl test (F.3) with initiation by a standard No 8 detonator (see Appendix 1 to the UN RTDG, Manual of Tests and Criteria) is ‘no’. In this case, the results of test 1 (a) and 2 (a) are deemed to be ‘-’.
2.1.4.3. A substance or mixture shall not be classified as explosive if:
(a) There are no chemical groups associated with explosive properties present in the molecule. Examples of groups which may indicate explosive properties are given in Table A6.1 in Appendix 6 of the ►M4  UN RTDG ◄ , Manual of Tests and Criteria; or
(b) The substance contains chemical groups associated with explosive properties which include oxygen and the calculated oxygen balance is less than - 200;

The oxygen balance is calculated for the chemical reaction:

CxHyOz+ [x+ (y/4)-(z/2)] O2 → x CO2 + (y/2) H2O

Using the formula:

Oxygen balance = -1 600 [2x + (y/2)-z]/molecular weight;

(c) When the organic substance or a homogenous mixture of organic substances contains chemical groups associated with explosive properties but the exothermic decomposition energy is less than 500 J/g and the onset of exothermic decomposition is below 500 °C. The exothermic decomposition energy can be determined using a suitable calorimetric technique; or
(d) For mixtures of inorganic oxidising substances with organic material(s), the concentration of the inorganic oxidising substance is:
less than 15 % by mass, if the oxidising substance is assigned to Categories 1 or 2;
less than 30 % by mass, if the oxidising substance is assigned to Category 3.
2.1.4.4. In the case of mixtures containing any known explosives, the acceptance procedure has to be performed.