Their results concluded that IAQ was not directly proportional to the reduction in the ventilation rate but rather due to a combination of factors including the ventilation system design,the control of local conditions,and the use of standard operating procedures specific to the laboratory operation.They found that a lower ventilation rate could be used without a major impact on the air quality in the occupird zone.Sandru et al found that the concentration below the imposed exposure limits could be achieved by 6 ACH in case of moderately hazardous chemicals through health hazard analysis.