ABSTRACT
This chapter describes the basic types of laboratory fume hoods, and the procedures for testing hoods. Included are testing air volume and velocity, smoke testing, and troubleshooting laboratory fume hoods for reverse air flow and incorrect face velocities. The air flow through the variable air volume conventional fume hood is variable in total air volume but has a constant face velocity. The auxiliary air fume hood has a movable, vertical or combination horizontal-vertical sash with auxiliary air ducted into the hood. The standard bypass hood has a movable, vertical or combination horizontal-vertical sash. The construction of the bypass hood is similar to the standard conventional hood described above with the addition of the bypass. Conduct the test with the normal hood apparatus in place and operating except where clearance must be provided for the test instruments or equipment. Reverse air flow in a fume hood can be caused by air currents in the room or eddy currents in the hood.
