3.1.

Procedure - For each test, two specimens of a sample unit (see paragraph 2.4.17.4. of UN Regulation No. 48) are taken. One specimen shall be stored in a dark and dry container for subsequent use as "reference unexposed specimen".
The second specimen shall be subjected to a source of illumination in accordance with ISO Standard 105 - B02 - 1978, Section 4.3.1; the retro-reflective material shall be exposed until blue standard No. 7 has faded to No. 4 on the grey scale and the fluorescent material until blue standard No. 5 has faded to No. 4 on the grey scale. After the test, the specimen shall be washed in a dilute neutral detergent solution, dried and examined for conformity with the requirements specified in paragraphs 3.2. to 3.4.

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