Chapter 2.3

Class 3 - Flammable liquids


Introductory note

The flashpoint of a flammable liquid may be altered by the presence of an impurity. The substances listed in class 3 in the Dangerous Goods List in chapter 3.2 shall generally be regarded as chemically pure. Since commercial products may contain added substances or impurities, flashpoints may vary, and this may have an effect on classification or determination of the packing group for the product. In the event of doubt regarding the classification or packing group of a substance, the flashpoint of the substance shall be determined experimentally.

Definitions and general provisions

Class 3 includes the following substances:

  1. flammable liquids (see and;

  2. liquid desensitized explosives (see

Flammable liquids are liquids, or mixtures of liquids, or liquids containing solids in solution or suspension (such as paints, varnishes, lacquers, etc., but not including substances which, on account of their other dangerous characteristics, have been included in other classes) which give off a flammable vapour at or below 60°C closed-cup test (corresponding to 65.6°C open-cup test), normally referred to as the "flashpoint". This also includes:

  1. liquids offered for transport at temperatures at or above their flashpoint; and

  2. substances transported or offered for transport at elevated temperatures in a liquid state, which give off a flammable vapour at temperatures equal to or below the maximum transport temperature.

However, the provisions of this Code need not apply to such liquids with a flashpoint of more than 35°C which do not sustain combustion. Liquids are considered to be unable to sustain combustion for the purposes of the Code if:

  1. they have passed the suitable combustibility test (see the Sustained Combustibility Test prescribed in part III, 32.5.2 of the Manual of Tests and Criteria); or

  2. their fire point according to ISO 2592:1973 is greater than 100°C; or

  3. they are water-miscible solutions with a water content of more than 90%, by mass.
Liquid desensitized explosives are explosive substances which are dissolved or suspended in water or other liquid substances, to form a homogeneous liquid mixture to suppress their explosive properties. Entries in the Dangerous Goods List for liquid desensitized explosives are UN 1204, UN 2059, UN 3064, UN 3343, UN 3357 and UN 3379.
Assignment of packing group
The criteria in are used to determine the hazard grouping of a liquid that presents a risk due to flammability.
For liquids whose only risk is flammability, the packing group for the substance is the hazard grouping shown in
For a liquid with additional risk(s), the hazard group determined from and the hazard group based on the severity of the additional risk(s) shall be considered, and the classification and packing group determined in accordance with the provisions in chapter 2.0.

Viscous flammable liquids such as paints, enamels, lacquers, varnishes, adhesives and polishes having a flash point of less than 23°C may be placed in packing group III in conformity with the procedures prescribed in the Manual of Tests and Criteria, part III, subsection 32.3, provided that:

  1. The viscosity1 and flash point are in accordance with the following table:

    Kinematic viscosity (extrapolated) v (at near-zero shear rate) mm2/s at 23°C Flow-time t in seconds Jet diameter (mm) Flashpoint (closed-cup) in °C
    20 < v ≤ 80 20 < t ≤ 60 4 above 17
    80 < v ≤ 135 60 < t ≤ 100 4 above 10
    135 < v ≤ 220 20 < t ≤ 32 6 above 5
    220 < v ≤ 300 32 < t ≤ 44 6 above -1
    300 < v ≤ 700 44 < t ≤ 100 6 above -5
    700 < v 100 < t 6 no limit
  2. less than 3% of the clear solvent layer separates in the solvent separation test;

  3. the mixture or any separated solvent does not meet the criteria for class 6.1 or class 8;

  4. the substances are packed in receptacles of not more than 30-litre capacity.
Substances classified as flammable liquids due to their being transported or offered for transport at elevated temperatures are included in packing group III.

Viscous liquids which:

  • have a flashpoint of 23°C or above and less than or equal to 60°C;

  • are not toxic or corrosive;

  • are not environmentally hazardous or are environmentally hazardous transported in single or combination packagings containing a net quantity per single or inner packaging of 5 litres or less, provided the packagings meet the general provisions of, and to;

  • contain not more than 20% nitrocellulose, provided the nitrocellulose contains not more than 12.6% nitrogen by dry mass; and

  • are packed in receptacles of not more than 30-litre capacity

are not subject to the provisions for the marking, labelling and testing of packages in chapters 4.1, 5.2 and 6.1, if:

  1. in the solvent separation test (see part III, 32.5.1 of the Manual of Tests and Criteria) the height of the separated layer of solvent is less than 3% of the total height; and

  2. the flowtime in the viscosity test (see part III, 32.4.3 of the Manual of Tests and Criteria) with a jet diameter of 6 mm is equal to or greater than:

    1. 60 s; or

    2. 40 s if the viscous liquids contains not more than 60% of class 3 substances.

The following statement shall be included in the transport document: "Transport in accordance with of the IMDG Code." (see

Hazard grouping based on flammability

Flammable liquids are grouped for packing purposes according to their flashpoint, their boiling point, and their viscosity. This table shows the relationship between two of these characteristics.

Packing group Flashpoint (closed cup) in °C (c.c.) Initial boiling point in °C
I - ≤ 35
II < 23 > 35
III ≥ 23 to ≤ 60 > 35

Determination of flashpoint

Note: The provisions of this section are not mandatory.

The flashpoint of a flammable liquid is the lowest temperature of the liquid at which its vapour forms an ignitable mixture with air. It gives a measure of the risk of formation of explosive or ignitable mixtures when the liquid escapes from its packing. A flammable liquid cannot be ignited so long as its temperature remains below the flashpoint.

Note: Do not confuse the flashpoint with the ignition temperature, which is the temperature to which an explosive vapour-air mixture must be heated to cause actual explosion. There is no relationship between the flashpoint and the ignition temperature.
The flashpoint is not an exact physical constant for a given liquid. It depends to some extent on the construction of the test apparatus used and on the testing procedure. Therefore, when providing flashpoint data, specify the name of the test apparatus.
Several standard apparatuses are in current use. They all operate on the same principle: a specified quantity of the liquid is introduced into a receptacle at a temperature well below the flashpoint to be expected, then slowly heated; periodically, a small flame is brought near to the surface of the liquid. The flashpoint is the lowest temperature at which a "flash" is observed.
The test methods can be divided into two groups, depending on the use in an apparatus of an open receptacle (open-cup methods) or a closed one which is only opened to admit the flame (closed-cup methods). As a rule, the flashpoints found in an open-cup test are a few degrees higher than in a closed-cup test.
In general, reproducibility in closed-cup apparatus is better than in open-cup.
It is therefore recommended that flashpoints, especially in the range around 23°C, shall be determined by means of closed-cup (c.c) methods.
Flashpoint data in this Code are generally based on closed-cup methods. In countries where it is customary to determine flashpoints by the open-cup method, the temperatures given by that method would need to be reduced to correspond with those in this Code.

Determination of flashpoint

The following methods for determining the flashpoint of flammable liquids may be used:

International standards:

  • ISO 1516
  • ISO 1523
  • ISO 2719
  • ISO 13736
  • ISO 3679
  • ISO 3680

National standards:

American Society for Testing Materials International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, Pennsylvania, USA 19428-2959:

  • ASTM D3828-07a, Standard Test Methods for Flash Point by Small Scale Closed Cup Tester
  • ASTM D56-05, Standard Test Method for Flash Point by Tag Closed Cup Tester
  • ASTM D3278-96(2004)e, Standard Test Methods for Flash Point of Liquids by Small Scale Closed-Cup Apparatus
  • ASTM D93-08, Standard Test Methods for Flash Point by Pensky-Martens Closed Cup Tester

Association française de normalisation, AFNOR, 11, rue Francis de Pressensé, 93571 La Plaine Saint-Denis Cedex:

  • French Standard NF M 07-019
  • French Standards NF M 07-011/NF T 30-050/NF T 66-009
  • French Standard NF M 07-036

Deutsches Institut für Normung, Burggrafenstr. 6, D-10787 Berlin:

  • Standard DIN 51755 (flashpoints below 65ºC)

State Committee of the Council of Ministers for Standardization, 113813, GSP, Moscow, M-49 Leninsky Prospect, 9:

  • GOST 12.1.044-84

Determination of initial boiling point

The following methods for determining the initial boiling point of flammable liquids may be used:

International standards:

  • ISO 3924
  • ISO 4626
  • ISO 3405

National standards:

American Society for Testing Materials International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, Pennsylvania, USA 19428-2959:

  • ASTM D86-07a, Standard Test Method for Distillation of Petroleum Products at Atmospheric Pressure
  • ASTM D1078-05, Standard Test Method for Distillation Range of Volatile Organic Liquids

Further acceptable methods:

  • Method A.2 as described in Part A of the Annex to Commission Regulation (EC) No 440/2008.2

Substances not accepted for transport

Chemically unstable substances of class 3 shall not be accepted for transport unless the necessary precautions have been taken to prevent the possibility of a dangerous decomposition or polymerization under normal conditions of transport. For the precautions necessary to prevent polymerization, see special provision 386 of chapter 3.3. To this end particular care shall be taken to ensure that receptacles and tanks do not contain any substances liable to promote these reactions.

Chapter 2.2

Chapter 2.4

  1. Viscosity determination: Where the substance concerned is non-Newtonian, or where a flow cup method of viscosity determination is otherwise unsuitable, a variable shear-rate viscometer shall be used to determine the dynamic viscosity coefficient of the substance, at 23 °C, at a number of shear rates. The values obtained are plotted against shear rate and then extrapolated to zero shear rate. The dynamic viscosity thus obtained, divided by the density, gives the apparent kinematic viscosity at near-zero shear rate.

  2. Commission Regulation (EC) No 440/2008 of 30 May 2008 laying down test methods pursuant to Regulation (EC) No 1907/2006 of the European Parliament and of the Council on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) (Official Journal of the European Union, No L 142 of 31.05.2008, pages 1-739 and No L 143 of 03.06.2008, page 55).