Chemical fume hoods are intended to remove vapors, gases, and dusts of toxic, flammable, corrosive or otherwise dangerous materials. With the sash lowered, laboratory fume hoods can also afford workers protection from such hazards as chemical splashes or sprays and fires. However, they are not designed to withstand explosions. Before performing hazardous operations, make simple checks to determine that the hood is working (e.g., a small piece of paper held at the face of the hood will be sucked inward). When work is being conducted within the hood, position the sash so that protection from splashes, flying debris, etc., is provided. Normally, this is a 12-16 inch work opening. Experimental procedures should be conducted well inside the hood. Moving an apparatus 5-10 cm back from the front edge into the hood can reduce the vapor concentration at the face by 90%. Hoods are not intended for the storage of chemicals. Materials stored in them should be kept to a minimum and in a manner that will not interfere with airflow. Hoods should be considered as backup safety devices that can contain and exhaust toxic, offensive, or flammable materials. They should not be regarded as a means of disposing of chemicals.
The use of perchloric acid requires specially designed Perchloric Acid Fume Hoods. For the specifications of a Perchloric Acid Fume Hood, as well as the requirements and procedures for installation, repair, removal and relocation, consult the Facilities Engineering Dept. or the DESHS.