5.1 This method is intended to induce property changes associated with end-use conditions, including the effects of solar radiation, moisture, and heat. The exposure used is not intended to simulate the deterioration caused by localized weather phenomena such as atmospheric pollution, biological attack, and saltwater exposure.

5.2 The relation between time to failure in an exposure conducted in accordance with this test method and service life in a specific outdoor environment requires determination of an acceleration factor, as defined in Terminology G113. The acceleration factor is material dependent and is only valid if it is based on data from a sufficient number of separate exterior and laboratory-accelerated exposures so that the results used to relate times to failure in each exposure can be analyzed using statistical methods.

Note 1: An example of a statistical analysis using multiple laboratory and exterior exposures to calculate an acceleration factor is described by J. A. Simms.4 See Practice G151 for more information and additional cautions about the use of acceleration factors.

5.2.1 The deterioration curve obtained from the results of this test method enables the user to determine the tendency of a geotextile to deteriorate when exposed to xenon arc radiation, water, and heat.

5.3 Variation in results may be expected when operating conditions are varied within the accepted limits of this test method. Its intended use is as a qualitative assessment of the presence of ultraviolet inhibitors, and comparison of that influence between products. However, no inference to the time of stability should be implied by the test results to the relation between time duration and outdoor exposure.

Note 2: Information on sources of variability and on strategies for addressing variability in the design, execution, and data analysis of laboratory-accelerated exposure tests is found in Guide G141.

5.3.1 If it becomes necessary for the purchaser and seller to use this test method for acceptance testing, the statistical bias, if any, between the purchaser's and seller's laboratories should be determined. Such comparison is based on specimens randomly drawn from the sample of geotextile being evaluated.

5.3.2 In such cases, at a minimum, the two parties should take a group of test specimens which are as homogeneous as possible, and which are from a lot of material of the type in question. The test specimens should then be randomly assigned in equal numbers to each laboratory for testing. The average results from the two laboratories should be compared using Student's t-test for unpaired data and an acceptable probability level chosen by the two parties before the testing started. If a bias is found, either its cause must be found and corrected, or the purchaser and the supplier must agree to interpret future test results in the light of the known bias.