The Containment Capacity of a fume hood represents its ability to keep the chemicals inside the enclo-sure and prevent them from returning into the room through the front sash.
It is tested with a tracer gas, actually SF6 (Sulfuric Hexafluoride), according to a method specified in the Ameri can Standard for the testing fume hoods, the ASHRAE 110. For the test, the fume hood ventilation is turned on and the sash opened at the height specified by the manufacturer to obtain a face velocity of 0,4 to 0,6 m/s*. Then the SF6 gas is emitted inside the enclosure at a rate of 4L per minute. A dum-my, simulating the chemist, is placed in front of the enclosure. A sensor, fixed at the nose level of the dummy and connected to an SF6 analyser which allows to measure continuously a possible escape of SF6 from the fume hood through the front sash. Another US Standard, the ANSI/AIHA Z9.5, specifies that the concentration of SF6 at the nose level of the dummy shall not
exceed 0,05ppm.
1、The European fume hood standard EN 14175 also specifies containment tests with SF6, but with a different procedure. If
interested please consult us.
2、Unlike what many customers think, the face velocity of 0,4 to 0,6 m/s at the sash opening level is not suffcient to guarantee the safety of a fume hood as chemicals vapors might go back into the lab against the airflow penetrating the hood.
Erlab filtration fume hoods offer a much safer containment than ducted fume hoods !
