Considers that the dispersed harmful gas will certainly mixe with a large amount of room air,the mixed gas density is effective relation density but a harmful gas density.

• 认为过去关于全面通风排风量在作业场所上下部的分配,相关设计规范和技术规定是根据有害物的气体密度来确定的,而忽略了有害物气体的允许浓度值。