[ possibility of applying less tracer gas in ASHRAE-110-95 method of hood performance test]

ABSTRACT

A considerable amount of sulfur hexafluoride is applied to evaluate the performance of each laboratory hood according to ASHRAE-110-95 method.SF [6] is extremely hostile to environment and expensive. In present work, the possibility of conducting this method of hood performance test with less volume of SF [6] was investigated. The performance of a laboratory hood was evaluated using ASHRAE110-95 standard method at three different ventilation capacity as well as three different volumetric flow rates of injected SF 6 while a mannequin was located at the front of hood. Face velocity was measured 180 times using a thermal anemometer TA-2 model.Air flow was visualized through injecting low and high volume of smokes at 18 tests. Sulfur hexafluoride was injected at three different volumetric flow rates of 2, 3 and 4 lit / min.The occupational exposure of a hypothetic hood operator was determined 27 times through direct reading. The average and standard deviation of face velocity at hood inlet were 0.42 +/- 0.04, 0.6 +/- 0.07, 0.7 +/- 0.11 m / s respectively, ranging from 0.36-1.1 m / s. the studied hood did not have an acceptable performance when tested with high volumes of smoke, but it did have an acceptable performance while it was tested with low volumes of smoke. The application of ASHRAE 110-95 hood performance test with smaller volume of tracer sulfur hexafluoride gas is not recommended.