ISO/IEC 22237-4:2021 This document addresses environmental control within data centres based upon the criteria and classifications for “availability”, “security” and “energy efficiency enablement” within ISO/IEC 22237-1. This document specifies requirements and recommendations for the following: a) temperature control; b) fluid movement control; c) relative humidity control; d) particulate control; e) vibration; f) physical security of environmental control systems.