This part of ISO 22975 is applicable to the determination of the long term behaviour and service life of selective solar absorbers for use in vented flat plate solar collectors working under conditions corresponding to that in a typical solar domestic hot water system or combisystem. This part of ISO 22975 specifies a failure criterion of a solar absorber based on changes in optical performance of the absorber. The optical properties of interest are solar absorptance and thermal emittance. This part of ISO 22975 specifies durability testing procedures focused on resistance to high temperatures and condensation of water on the absorber surface as well as high humidity in the presence of sulfur dioxide.