Spray aerosol: Ignition distance and enclosed space ignition test (UN Class 2)

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Spray aerosol: Ignition distance and enclosed space ignition test (UN Class 2)

This test is used to classify spray aerosols as non-flammable, flammable or extremely flammable. For spray aerosols, the evaluation is based on the flame length in the ignition distance test and, if applicable, the time equivalent or deflagration density in the enclosed space ignition test.

Ignition distance test for spray aerosols

This test is used for aerosols with a spray distance of ≥ 15 cm and more.

The aerosol is sprayed in the direction of an ignition source which is placed in each case at a distance interval of 15 cm (Figure 2). The aerosol is observed to determine whether it ignites and a sustained flame is produced. An ignition and sustained combustion is defined as a stable flame that persists for at least 5 s. The ignition source is a gas burner with a blue, non-luminescent flame 4-5 cm in height.

If no ignition is observed during this test, the enclosed space ignition test must additionally be performed.

The classification is made as follows:

  • The aerosol is classified as extremely flammable if ignition occurs at a distance ≥ 75 cm.
  • The aerosol is classified as flammable if ignition occurs at 15 cm ≤ distance < 75 cm.
  • If no ignition or ignition < 15 cm occurs in the ignition distance test, the result of the enclosed space ignition test is decisive.

Enclosed space ignition test for spray aerosols

This test is used for aerosols with a spray distance ≥ 15 cm, provided no ignition occurred in the ignition distance test.
The contents of a pressurized aerosol dispenser are sprayed into a cylindrical test vessel containing a burning candle (Figure 5). If an observable ignition occurs, the elapsed time and discharged mass of aerosol are noted to evaluate the ignitability of the aerosol spray.

The classification is as follows:

  • The aerosol shall be classified as flammable if the time equivalent in the enclosed space ignition test is ≤ 300 s/m3 or the deflagration density is ≤ 300 g/m3.
  • Otherwise, the aerosol is classified as non-flammable. For this classification, an enthalpy of combustion of < 20 kJ/g must also have been determined. If the enthalpy of combustion is ≥ 20 kJ/g, the aerosol is to be classified as flammable, regardless of the result of the enclosed space ignition test.

The time equivalent is calculated according to:

And the deflagration density is calculated according to:

Test setup for the ignition distance test – Figure 31.4.1 from UN Tests and Criteria Spray aerosol: Ignition distance and enclosed space ignition test (UN Class 2)
Figure 2: Test setup for the ignition distance test – Figure 31.4.1 from UN Tests and Criteria
Figure 3 Test vessel for enclosed space ignition test – Figure 31.5.1 from UN Tests and Criteria Spray aerosol: Ignition distance and enclosed space ignition test (UN Class 2)
Figure 3 Test vessel for enclosed space ignition test – Figure 31.5.1 from UN Tests and Criteria
Candle for enclosed space ignition test – Figure 31.5.2 from UN Tests and Criteria Spray aerosol: Ignition distance and enclosed space ignition test (UN Class 2)
Figure 4 Candle for enclosed space ignition test – Figure 31.5.2 from UN Tests and Criteria
Candle for enclosed space ignition test in its metal support – Figure 31.5.3 from UN Tests and Criteria Spray aerosol: Ignition distance and enclosed space ignition test (UN Class 2)
Figure 5: Candle for enclosed space ignition test in its metal support – Figure 31.5.3 from UN Tests and Criteria