Important laboratory fume hood guidelines

A safety message from USU Environmental Health and Safety

Work involving hazardous and noxious materials that are toxic, odoriferous, volatile or harmful should be conducted within a chemical fume hood. The chemical fume hood in your laboratory functions to capture, retain and discharge noxious or hazardous vapors, fumes and dusts generated within it. It is not intended to capture contaminants generated elsewhere in the room.

Laboratory fume hoods and adjacent work areas should be kept clean and free of debris at all times. Solid objects and materials (such as paper) should be kept from entering the exhaust ducts of the hoods. Objects lodged in ducts or fans will adversely affect the systems operation. Also, the hood will have better airflow across the work surface if there are minimal numbers of bottles, beakers and laboratory apparatus inside the hood; therefore, it is prudent to keep unnecessary equipment and glassware outside

 The following is a list of guidelines for the proper use of your chemical fume hood:

Always assure the hood is operational before initiating an experiment. Unless a hood is fully functional it should not be used. If the air flow has ceased, close sash and call Facilities at 797-1947. Fume hood alarms should never be tampered with, bypassed, disengaged or turned OFF. Be aware that the alarms are in place to alert the user to a potential issue with the hood. All Low Flow Alarms should be reported to the Facilities at 797-1947.

Fume hoods are NOT to be used as permanent storage for chemicals or equipment. The purpose and function of a hood is NOT to store chemicals or unused items. The fume hood is NOT a storage cabinet. All chemicals utilized in the lab should be stored in an appropriate storage cabinet.

Minimize activity in front of the hood. Avoid creation of strong cross drafts (greater than 100 fpm) caused by open windows and doors or pedestrian traffic. Keep windows and doors shut and pedestrian traffic, in front of the hood, to a minimum. Drafts will pull contaminants from the hood into the laboratory.

Do not work in the hood with the sash fully open. While performing work in the hood the sliding sash should be kept at the height designated sixteen inches (16″). This allows the sash to serve as a physical barrier between your face and the contents of the fume hood should a spill, splash, explosion or fire occur. When not in use, the sash should be kept closed.

Solid objects placed at the face of the hood cause turbulence in the air flow. Turbulence reduces the capture efficiency of the hood and increases the chance of contaminant release into the lab environment. Only items necessary to perform the current experiment should be in the hood. Place equipment, materials, etc. back 6″ from the face and avoid blocking the rear baffle. Large objects should be placed on blocks 2-3″ above the work surface to allow air flow under and around the object. The more equipment in the hood, the greater the air turbulence and the chance for gaseous escape in the lab.

Avoid placing your head in the fume hood. Once your head has gone past the plane of the sash you are inside the hood with the chemicals.

All fume hoods should be inspected annually by EH&S. If your fume hood has not been inspected within the last year or if you have any questions, please call (7-2892).

Other things to keep in mind…

  • Perform work in a chemical fume hood whenever feasible.
  • Fume hood alarms should NEVER be tampered with, bypassed, disengaged or turned off.
  • No electrical outlets should be located inside the hood.
  • Always wear appropriate PPE (gloves, goggles, lab coats, etc.) when working with chemicals.
  • Do not use infectious materials in a chemical fume hood.
  • Keep the sash glass clean. Never obstruct your view with paper, notices, decals or other items on the sashes.
  • Radioactive materials may not be used in the hoods without prior approval of the Radiological Safety Officer.
  • Routine maintenance on the fume hood will need to be performed. This may require one or more fume hoods to be shut down. Depending on the type of repair, your cooperation will be required in sealing and removing all chemicals to prevent exposure of maintenance workers.
  • Never use perchloric acid in a hood that is not designed for this use. Perchloric acid can leave explosive residues in a fume hood, duct system or on a fan. Perchloric acid also forms explosive mixtures with organic compounds. Perchloric acid hoods have a wash-down feature which should be used after each use of the hood and at least every two weeks when the hood is not in use. The date of each wash down should be recorded by laboratory personnel.
  • Hoods should not be used to evaporate toxic or irritating chemicals. Fume hoods are designed to remove small quantities of vapor and gas which might escape during laboratory operations. If vaporization of large quantities of such materials is a necessary part of the operation, a means of collecting the vapor by distillation or scrubbing should be considered, rather than allowing it to escape through the hood vent. The collected liquid can then be disposed of as a liquid waste.

Rachel Curry, Environmental Health and Safety