47 Laboratory Safety Manual Environmental Health and Safety display shows a number outside this range. If a hood does not have a monitor, a tissue can be taped to the bottom of the hood sash. If the tissue is continuously pulled inside the hood, it can be assumed that the fume hood is properly operating. • Set the sash at or below (18 inches) the arrow sticker on the side of the hood face. • Replace the sash or panels that may have been temporarily removed to set up an experiment. • Raise large equipment one to two inches so that air can flow under the unit. Equipment placed directly on the work surface may impede airflow into the hood. • Ensure that the baffles (rear panels inside the hood) are not blocked. • Eliminate sources that may create a cross-draft at the face of the hood (fans, open doors, or windows). • Do not modify the hood design without approval from the manufacturer. • Remove spark producing sources from the hood when flammable liquids or gases are present. While working in hood: • Do not put head inside hood. • Avoid rapid arm and body movements. • Conduct work at a minimum of six inches from the hood sash. • Request that other laboratory personnel minimize travel in front of the hood. • Do not obstruct any hood openings. • Fume hoods must never be used to evaporate waste materials. • Reduce/limit the amount of items on the work surface for proper air flow (chemicals, equipment, flasks, paper) After working in the hood: • Clean the work surface. • Limit storage of materials in hood – too many items in a hood disrupts proper airflow. • Close all containers in the hood. • Lower the sash and turn off the interior light. • Ductless fume hoods are prohibited at Iowa State University. Contact EH&S for more information. • Noise coming from the hood is a poor indicator that a fume hood is functioning properly.