2.2.2. Classification criteria
2.2.2.1. A flammable gas is classified in Category 1A, 1B or 2 in accordance with Table 2.2.1. Flammable gases that are pyrophoric and/or chemically unstable are always classified in Category 1A.
Table 2.2.1
Criteria for categorisation of flammable gases
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Category |
Criteria |
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1A |
Flammable gas |
Gases, which at 20 °C and a standard pressure of 101,3 kPa are: (a) ignitable when in a mixture of 13 % or less by volume in air; or (b) have a flammable range with air of at least 12 percentage points regardless of the lower flammability limit unless data show they meet the criteria for Category 1B |
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Pyrophoric gas |
Flammable gases that ignite spontaneously in air at a temperature of 54 °C or below |
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Chemically unstable gas |
A |
Flammable gases which are chemically unstable at 20 °C and a standard pressure of 101,3 kPa |
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B |
Flammable gases which are chemically unstable at a temperature greater than 20 °C and/or a pressure greater than 101,3 kPa |
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1B |
Flammable gas |
Gases which meet the flammability criteria for Category 1A, but which are not pyrophoric, nor chemically unstable, and which have at least either: (a) a lower flammability limit of more than 6 % by volume in air; or (b) a fundamental burning velocity of less than 10 cm/s; |
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2 |
Flammable gas |
Gases, other than those of Category 1A or 1B, which, at 20 °C and a standard pressure of 101,3 kPa, have a flammable range while mixed in air. |
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NOTE 1: Aerosols shall not be classified as flammable gases. See Section 2.3.
NOTE 2: In the absence of data allowing classification into Category 1B, a flammable gas that meets the criteria for Category 1A is classified by default in Category 1A.
NOTE 3: Spontaneous ignition for pyrophoric gases is not always immediate, and there may be a delay.
NOTE 4: In the absence of data on its pyrophoricity, a flammable gas mixture shall be classified as a pyrophoric gas if it contains more than 1 % (by volume) of pyrophoric component(s).