These recommendations cover the basic criteria for the design of aircraft cabin pressurization control systems as follows: 1. To ensure aircraft safety 2. Physiology and limits which govern maximum permissible pressure time relations as related to aircraft passenger comfort. 3. General pressurization control system performance requirements design to satisfy (2). 4. Technical considerations relevant to satisfying (3). The purpose of the recommended practice is to provide the aerospace industry with guidelines as to the pertinent technology relating to the physiological consideration, the technical system requirements and design objectives for aircraft pressurization control systems. This recommended practice is applicable to pressurized aircraft regardless of the number of passengers or crew. The pressurization control system must provide maximum safety and passenger and crew comfort as a result of changes in cabin pressure altitude during the entire aircraft flight and during ground operation.