46 Laboratory Safety Manual Environmental Health and Safety Appendix: Chemical Fume Hoods Chemical fume hoods are designed to protect personnel and prevent contaminants from escaping into the laboratory environment. All fume hoods work by drawing air from the room and into the fume hood. This air, along with the chemical vapors and particulates, are then drawn up a duct and expelled out of the building. Interference with this airflow can compromise the hood’s ability to protect the user. The following chemical fume hood types are approved for use on campus: 1. Chemical fume hoods are intended to capture, contain, and exhaust fumes, vapors, and particulate matter generated when working with chemicals. A fume hood should be used when: • handling chemicals with inhalation hazards such as toxic gases, vapors, and powders • conducting procedures with exothermic reactions • handling chemicals with significant vapor pressure • handling flammable materials • working with compounds that have an offensive odor or have an unknown toxicity 2. Perchloric acid fume hoods are dedicated chemical fume hoods designed specifically for the use of perchloric acid. These hoods are installed with wash-down systems that prevent the formation of explosive perchlorates. 3. Radioisotope fume hoods are chemical fume hoods that have been authorized by Environmental Health and Safety (EH&S) for use with radioactive materials. Ductless fume hoods are prohibited at Iowa State University (ISU). Contact EH&S for more information. The following are NOT classified as fume hoods and are NOT to be used as a fume hood: • biosafety cabinets • laminar flow cabinets/clean benches • canopy hoods • receiving hoods Safe Work Practices Before beginning work in the hood: • Ensure that the hood has passed its annual certification. This will be indicated by a ‘Pass’ or ‘Fail’ on the certification card located on the fume hood. • Verify that the hood is functioning properly – check that air is flowing into the hood (monitor, magnahelic gauge, or simply observe the direction of a tissue attached to the sash). For fume hoods that have a face velocity monitor, the monitor should read between 80 – 125 feet per minute (fpm). Contact EH&S if the Chemical Fume Hood Certification Log Fume Hood
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