Part 4 of the standard considers the corrosive and erosive industrial environment to which land-based and off-shore, industrial-process measurement and control systems or parts of systems may be exposed during operation, during periods when they are installed but inactive, during storage or transportation. Maintenance and repair conditions are excluded from this part. The environmental influences considered in this part are limited to those which may directly affect performance of process-measurement and control systems or parts of such systems. Effects of the specific environmental conditions on personnel are not within the scope of this part. The appropriate values of the physical or chemical parameters listed here as well as the qualitative descriptions of the environment should be used to define local environments in which equipment is expected to operate, be transported and stored. Only conditions as such are considered; the resulting effects of these conditions on instrument performance are specifically excluded. Many environmental conditions listed in this part are difficult to classify so that a qualitative description is used to characterize the environment.