I ratings provide a measure of the ignitability and flammability properties of a product.
The I Rating tests are utilised when the dimensi*** and the geometrical form of the article do not permit the sampling of the test pieces, which are necessary for the determination of the M classification according to documentation sheet P 92-507.
The material is subjected to the following two tests for reaction to fire:
· Determination of the oxygen index according to EN ISO 4589 Part 2
· Glow Wire Test according to the requirements of EN 60695-2-11
EN ISO 4589 Part 2 (Oxygen Index) Test
This Part of EN ISO 4589 specifies methods for determining the minimum concentration of oxygen, in admixture with nitrogen that will support combustion of ***all vertical test specimens under specified test conditi***. The test is performed at an ambient temperature of 23°C &plu***n; 2°C. The results are defined as oxygen index values.
Principle – A ***all test specimen is supported vertically in a mixture of oxygen and nitrogen flowing upwa*** through a transparent chimney. The upper end of the specimen is ignited and the subsequent burning beh***iour of the specimen is observed to compare the period for which the burning continues, or the length of the specimen burnt, with specified limits for such burning. By testing a series of specimens in different oxygen concentrati***, the minimum oxygen concentration is determined.
EN 60695-2-11 – Glow Wire Test
This part of EN ISO 60695-2-11 specifies methods to determine the performance of a material in its end use form when it is subjected to the conditi*** of the test specified in EN 60695-2-11: 2001.
Principle – A ***all specimen is subjected to a heated glowing wire h***ing a ‘U’ shape. The glowing wire is heated to a given temperature and then the test specimen is drawn towa*** it at a given force. The wire is applied for a period of 30 seconds and a number of observati*** are recorded.
The specimen is c***idered to h***e satisfactorily withstood the glow-wire test if there is no ignition of the test specimen or if there is ignition of the test specimen, the flames must cease within the allowed time following removal of the glowing wire and there shall be no ignition of the specified layer placed beneath the test specimen.
Calculation of I rating.
Utilising the guidance detailed in STM-S-001 the I Rating of a product is determined by assessing the test results against the criteria set out in the below table.
Table 1 of NF F 16-101
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Class
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Results of tests
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Oxygen Index
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Glow Wire
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I0
I1
I2
I3
I4
NC (1)
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≥ 70
≥ 45
≥ 32
≥ 28
≥ 20
< 20
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No Ignition at 960°C
No Ignition at 960°C
No Ignition at 850°C
Ignition does not persist at 850°C after glow wire is withdrawn.
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(1) NC: Non-classified
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