Assignment of packing groups

Flammable solids classified under the various entries in Table A of Chapter 3.2 shall be assigned to
packing groups II or III on the basis of test procedures of the Manual of Tests and Criteria, Part III,
sub-section 33.2.1, in accordance with the following criteria:
(a) Readily flammable solids which, when tested, have a burning time of less than 45 seconds over
a measured distance of 100 mm shall be assigned to:
Packing group II: if the flame passes the wetted zone;
Packing group III: if the wetted zone stops the flame for at least four minutes;
(b) Metal powders or powders of metal alloys shall be assigned to:
Packing group II: if, when tested, the reaction spreads over the whole length of the sample
in five minutes or less;
Packing group III: if, when tested, the reaction spreads over the whole length of the sample
in more than five minutes.
For solids which may cause fire through friction, the packing group shall be assigned by analogy with
existing entries or in accordance with any special provision.

 

Self-reactive substances Definitions

For the purposes of ADR, self-reactive substances are thermally unstable substances liable to undergo
a strongly exothermic decomposition even without participation of oxygen (air). Substances are not
considered to be self-reactive substances of Class 4.1, if:
(a) they are explosives according to the criteria of Class 1;
(b) they are oxidizing substances according to the classification procedure for Class 5.1
(see 2.2.51.1) except that mixtures of oxidizing substances which contain 5% or more of
combustible organic substances shall be subjected to the classification procedure defined in
Note 2;
(c) they are organic peroxides according to the criteria of Class 5.2 (see 2.2.52.1);
(d) their heat of decomposition is less than 300 J/g; or
(e) their self-accelerating decomposition temperature (SADT) (see Note 3 below) is greater than
75 °C for a 50 kg package.
NOTE 1: The heat of decomposition can be determined using any internationally recognised method
e.g. differential scanning calorimetry and adiabatic calorimetry.
NOTE 2: Mixtures of oxidizing substances meeting the criteria of Class 5.1 which contain 5% or
more of combustible organic substances, which do not meet the criteria mentioned in (a), (c), (d) or
(e) above, shall be subjected to the self-reactive substance classification procedure.
A mixture showing the properties of a self-reactive substance, type B to F, shall be classified as a selfreactive
substance of Class 4.1.
A mixture showing the properties of a self-reactive substance, type G, according to the principle given
in section 20.4.3 (g) of Part II of the Manual of Tests and Criteria shall be considered for
classification as a substance of Class 5.1 (see 2.2.51.1).
NOTE 3: The self-accelerating decomposition temperature (SADT) is the lowest temperature at which
self-accelerating decomposition may occur with a substance in the packaging as used during
carriage. Requirements for the determination of the SADT are given in the Manual of Tests and
Criteria, Part II, Chapter 20 and section 28.4.
NOTE 4: Any substance which shows the properties of a self-reactive substance shall be classified as
such, even if this substance gives a positive test result according to 2.2.42.1.5 for inclusion in
Class 4.2.

Properties

The decomposition of self-reactive substances can be initiated by heat, contact with catalytic
impurities (e.g. acids, heavy-metal compounds, bases), friction or impact. The rate of decomposition
increases with temperature and varies with the substance. Decomposition, particularly if no ignition
occurs, may result in the evolution of toxic gases or vapours. For certain self-reactive substances, the
temperature shall be controlled. Some self-reactive substances may decompose explosively,
particularly if confined. This characteristic may be modified by the addition of diluents or by the use
of appropriate packagings. Certain self-reactive substances burn vigorously. Self-reactive substances
are, for example, some compounds of the types listed below:
aliphatic azo compounds (-C-N=N-C-);
organic azides (-C-N3);
diazonium salts (-CN2
+ Z-);
N-nitroso compounds (-N-N=O); and
aromatic sulphohydrazides (-SO2-NH-NH2).
This list is not exhaustive and substances with other reactive groups and some mixtures of substances
may have similar properties.

 

Classification

Self-reactive substances are classified into seven types according to the degree of danger they present.
The types of self-reactive substances range from type A, which is not accepted for carriage in the
packaging in which it is tested, to type G, which is not subject to the provisions for self-reactive
substances of Class 4.1. The classification of types B to F is directly related to the maximum quantity
allowed in one packaging. The principles to be applied for classification as well as the applicable
classification procedures, test methods and criteria and an example of a suitable test report are given
in Part II of the Manual of Tests and Criteria.

Self-reactive substances which have already been classified and are already permitted for carriage in
packagings are listed in 2.2.41.4, those already permitted for carriage in IBCs are listed in 4.1.4.2,
packing instruction IBC520 and those already permitted for carriage in tanks according to Chapter 4.2
are listed in 4.2.5.2, portable tank instruction T23. Each permitted substance listed is assigned to a
generic entry of Table A of Chapter 3.2 (UN Nos. 3221 to 3240), and appropriate subsidiary risks and
remarks providing relevant transport information are given.
The collective entries specify:
- self-reactive substances types B to F, see 2.2.41.1.11 above;
- physical state (liquid/solid); and
- temperature control (when required), see 2.2.41.1.17 below.
The classification of the self-reactive substances listed in 2.2.41.4 is based on the technically pure
substance (except where a concentration of less than 100% is specified).

Classification of self-reactive substances not listed in 2.2.41.4, 4.1.4.2, packing instruction IBC520 or
4.2.5.2, portable tank instruction T23 and assignment to a collective entry shall be made by the
competent authority of the country of origin on the basis of a test report. The statement of approval
shall contain the classification and the relevant conditions of carriage. If the country of origin is not a
Contracting Party to ADR, the classification and the conditions of carriage shall be recognized by the
competent authority of the first country Contracting Party to ADR reached by the consignment.

Activators, such as zinc compounds, may be added to some self-reactive substances to change their
reactivity. Depending on both the type and the concentration of the activator, this may result in a
decrease in thermal stability and a change in explosive properties. If either of these properties is
altered, the new formulation shall be assessed in accordance with the classification procedure.

Samples of self-reactive substances or formulations of self-reactive substances not listed in 2.2.41.4,
for which a complete set of test results is not available and which are to be carried for further testing
or evaluation, shall be assigned to one of the appropriate entries for self-reactive substances type C
provided the following conditions are met:
- the available data indicate that the sample would be no more dangerous than self-reactive
substances type B;
- the sample is packaged in accordance with packing method OP2 and the quantity per transport
unit is limited to 10 kg;
- the available data indicate that the control temperature, if any, is sufficiently low to prevent any
dangerous decomposition and sufficiently high to prevent any dangerous phase separation.

Desensitization

In order to ensure safety during carriage, self-reactive substances are in many cases desensitized by
use of a diluent. Where a percentage of a substance is stipulated, this refers to the percentage by mass,
rounded to the nearest whole number. If a diluent is used, the self-reactive substance shall be tested
with the diluent present in the concentration and form used in carriage. Diluents which may allow a
self-reactive substance to concentrate to a dangerous extent in the event of leakage from a packaging
shall not be used. Any diluent shall be compatible with the self-reactive substance. In this regard,
compatible diluents are those solids or liquids which have no detrimental influence on the thermal
stability and hazard type of the self-reactive substance. Liquid diluents in formulations requiring
temperature control (see 2.2.41.1.14) shall have a boiling point of at least 60 °C and a flash-point not
less than 5 °C. The boiling point of the liquid shall be at least 50 °C higher than the control
temperature of the self-reactive substance.

Temperature control requirements

Certain self-reactive substances may only be carried under temperature controlled conditions. The
control temperature is the maximum temperature at which the self-reactive substance can be safely
carried. It is assumed that the temperature of the immediate surroundings of a package only exceeds
55 °C during carriage for a relatively short time in a 24 hour period. In the event of loss of
temperature control, it may be necessary to implement emergency procedures. The emergency
temperature is the temperature at which such procedures shall be implemented.
The control and emergency temperatures are derived from the SADT (see table 1). The SADT shall
be determined in order to decide whether a substance shall be subjected to temperature control during
carriage. Provisions for the determination of the SADT are given in the Manual of Tests and Criteria,
Part II, Chapter 20 and Section 28.4.
Table 1: Derivation of control and emergency temperatures

Type of receptacle

SADT a

Control temperature

Emergency temperature

Single packagings and IBCs

20 °C or less

20 °C below SADT

10 °C below SADT

over 20 °C to 35 °C

15 °C below SADT

10 °C below SADT

over 35 °C

10 °C below SADT

5 °C below SADT

Tanks

not greater than 50 °C

10 °C below SADT

5 °C below SADT

 
a SADT of the substance as packaged for carriage.
Self-reactive substances with an SADT not greater than 55 °C shall be subject to temperature control
during carriage. Where applicable, control and emergency temperatures are listed in 2.2.41.4. The
actual temperature during carriage may be lower than the control temperature but shall be selected so
as to avoid dangerous separation of phases.

 

Solid desensitized explosives

Solid desensitized explosives are substances which are wetted with water or alcohols or are diluted
with other substances to suppress their explosive properties. Such entries in Table A of Chapter 3.2
are: UN Nos. 1310, 1320, 1321, 1322, 1336, 1337, 1344, 1347, 1348, 1349, 1354, 1355, 1356, 1357,
1517, 1571, 2555, 2556, 2557, 2852, 2907, 3317, 3319, 3344, 3364, 3365, 3366, 3367, 3368, 3369,
3370, 3376, 3380 and 3474.

Substances related to self-reactive substances

Substances that:
(a) have been provisionally accepted into Class 1 according to Test Series 1 and 2 but exempted
from Class 1 by Test Series 6;
(b) are not self-reactive substances of Class 4.1; and
(c) are not substances of Classes 5.1 or 5.2;
are also assigned to Class 4.1. UN Nos. 2956, 3241, 3242 and 3251 are such entries.

Polymerizing substances

Polymerizing substances are substances which, without stabilization, are liable to undergo a strongly
exothermic reaction resulting in the formation of larger molecules or resulting in the formation of
polymers under conditions normally encountered in carriage. Such substances are considered to be
polymerizing substances of Class 4.1 when:
(a) their self-accelerating polymerization temperature (SAPT) is 75 °C or less under the conditions
(with or without chemical stabilization as offered for carriage) and in the packaging, IBC or
tank in which the substance or mixture is to be carried;
(b) they exhibit a heat of reaction of more than 300 J/g; and
(c) they do not meet any other criteria for inclusion in classes 1 to 8.
A mixture meeting the criteria of a polymerizing substance shall be classified as a polymerizing
substance of Class 4.1.

Temperature control requirements

Polymerizing substances are subject to temperature control in carriage if their self-accelerating
polymerization temperature (SAPT) is:
(a) when offered for carriage in a packaging or IBC, 50 °C or less in the packaging or IBC in
which the substance is to be carried; or
(b) When offered for carriage in a tank, 45 °C or less in the tank in which the substance is to be
carried.

Substances not accepted for carriage

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