Optical instruments are affected during their use by a number of different environmental parameters which they are required to resist without significant reduction in performance and to remain within defined specifications. The type and severity of these parameters depend on the conditions of use of the instrument (for example, in the laboratory or workshop) and on its geographical location. The environmental effects on optical instrument performance in the tropics and subtropics are totally different from those found when they are used in arctic regions. Individual parameters cause a variety of different and overlapping effects on instrument performance. The manufacturer attempts to ensure, and the user naturally expects, that instruments will resist the likely rigours of their environment throughout their life. This expectation can be assessed by exposure of the instrument to a range of simulated environmental parameters under controlled laboratory conditions. This part of ISO 9022 specifies the methods relating to the environmental tests of optical instruments including additional assemblies from other fields (for example mechanical, chemical, and electronic devices), under equivalent conditions, for their ability to resist the influence of blowing dust. The purpose of testing is to investigate to what extent the optical, climatic, mechanical, chemical, and electrical (including electrostatic) performance characteristics of the specimen are affected by blowing dust, especially with a view to malfunctions of moving parts (such as sliding surfaces, bearings, contacts, operating controls, gears) or unacceptable wear of surfaces. Working Committee NA 027-01-02-03 AK "Umweltbedingungen und -prüfungen für optische Geräte" ("Environmental requirements and test methods for optical instruments") at DIN Standards Committee Optics and Precision Mechanics is responsible for this standard.