This part of ISO 9022 specifies methods for the testing of optical instruments and instruments containing optical components under equivalent conditions, for their ability to resist drip or rain. The purpose of testing is to investigate to what extent the optical, thermal, mechanical, chemical and electrical performance characteristics of the specimen are affected by drip or rain. Contamination of drip or rain water due to impurities in the air shall be ignored for the purposes of this part of ISO 9022.