本文件给出: 对地球大气成分的描述； 对人类呼吸生理学的描述； 二氧化碳和氧气对人体生理影响的生物医学文献综述； 氧气或二氧化碳的分压可能与海平面上的分压不同的环境情况的例子。 本文件确定了氧气和二氧化碳浓度限值以及预计不会造成生理痛苦的时间长度。为了充分说明对人体生理学的影响，本文件讨论了遇到低分压的高海拔暴露和涉及高分压条件的水下潜水。还包括呼吸器的使用和可以佩戴RPD的各种工作速率。

This document gives:

• a description of the composition of the Earth's atmosphere;
• a description of the physiology of human respiration;
• a survey of the current biomedical literature on the effects of carbon dioxide and oxygen on human physiology;
• examples of environmental circumstances where the partial pressure of oxygen or carbon dioxide can vary from that found at sea level.

This document identifies oxygen and carbon dioxide concentration limit values and the length of time within which they would not be expected to impose physiological distress. To adequately illustrate the effects on human physiology, this document addresses both high altitude exposures where low partial pressures are encountered and underwater diving, which involves conditions with high partial pressures. The use of respirators and various work rates during which RPD can be worn are also included.