Background and Aim: Laboratory fume-hoods are the first-level protection for the laboratory staff against hazardous chemical pollutants. Considering the large numbers of personnel, especially in petrochemical industry laboratories, this project was carried out in order to assess the performance of laboratory hoods based on tracer gas (SF6).

Materials and Methods: In this project 22 hoods in the laboratories of a petrochemical industry were studied. Operation of the hoods was assessed based on quantitative (with SF6 as tracer gas) and qualitative (face velocity measurement, using thermal anemometer) tests, according to ASHRAE 110 stndard.

Results: In comparison with the minimum acceptable face velocity (80 fpm), the mean values of face velocities of only 9.09% of the hoods passed the test (P=0.001) and were at an acceptable level. As regards the tracer gas test, the results were even worse: only 4.5% of the hoods passed the acceptability test (p=0.001). In addition, non of the hoods having an acceptable face velocity passed the tracer gas test. Similarly, no hood with an accepatable tracer gas performance had an acceptable face velocity.

Conclusion: Since there is no consistency between face velocity and tracer gas tests, performance of laboratory hoods can necessarily be assessed on the basis of the tracer gas quantitative test. The face velocity test is a supplementary test, which, if used alone wil give false results.