Abstract: In light of the special plateau conditions, the effect of O₂, CO₂and other harmful gases on human body is analyzed and the applicability of "Safety Rules for Metal and Non-Metal Mines" to the high altitude areas discussed. For areas above 2000m, it is suggested to use the equivalent altitude for setting the minimum concentration of O₂, and the formula for equivalent altitude is proposed. In respect to the human body's sensitivity to partial pressure of CO₂, the exposure limit expressed by mass concentration can satisfy the requirement. For some harmful gases, it is suggested to classify their exposure limits based on altitude.

Key words: Highland, Air quality standard, Equivalent altitude, Harmful gases