1. Scope 1.1 This practice covers the baic principals and operating procedures for using an enclosed carbon arc light and water apparatus to reproduce the weathering effects, which occur when materials are exposed in actual end use environments to direct sunlight and moisture as rain or dew or to sunlight through window glass. This practice is limited to the method of obtaining, measuring, and controlling the conditions and procedures of exposure. It does not specify the exposure conditions best suited for the material to be tested. 1.2 Test specimens are exposed to enclosed carbon arc light under controlled environmental conditions. 1.3 Specimen preparation an evaluation of the results are covered in various methods or specifications for specific materials. General guidance is given in Practice G 151 and ISO 4892-1. More specific information about methods for determining the change in properties after exposure and reporting these results is described in ISO 4582. 1.4 The values stated in SI units are to be regarded as the standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.