This paper made some investigation about the permissibleconcentration limits about contaminations in roadway tunnel from the point of view of the effects on the body.
The minimum permissible oxygen concentration for unprotected personnel is 19.5%, while the maximum is23.5%.
对于没有受到保护的人来说，允许的最小氧浓度是19.5%，最大是23.5%。
3
This Standard specifies the supreme permissible effluent concentration of flue dust, SO2 and nitrogen oxides as well as the emission limits of flue gas blackness by age limits.