Fume Hood Operations

Question

When should you use a fume hood?

Answer

You should use a fume hood when dealing with chemicals or substances that produce hazardous or irritating smells or fumes. Any chemical that is volatile, toxic, or irritating should be used within the working area of a fume hood.

Fume hoods are ventilated enclosures in which gases, vapors, and fumes are captured and removed from the working space. Exhaust fans are positioned on the roof of the building to pull air and contaminants through the ductwork to be dispersed into the atmosphere. The picture below depicts the basic design of a fume hood. Questions about how a fume hood works or training requests can be submitted to ehs@usd.edu

 

Safety tips

  • Air flow within the working space should be between on average 80-100 fpm. Many hoods come equipped with an alarm that will sound when the hood flow is outside of this range
  • The sash should be opened to approximately 8” to allow the user to reach underneath it into the work area, but protect the upper torso and face from exposure
  • If your fume hood has a combination of horizontally and vertically moving glass panels in the front sash, the horizontally moving panels should be as closed as possible before lifting the sash vertically
  • Hood sashes should be shut when not in use to stabilize air flow throughout the building, as multiple hoods likely utilize the same ductwork. This will prevent overtaxing the rooftop exhaust fans
  • To minimize exposure, keep and use all chemicals and equipment at least six inches back from the front of the fume hood sash
  • For better airflow, use equipment with legs or utilize risers to allow airflow underneath where you are working
  • Do not block the opening under the front airfoil
  • Never place sparking, or ignition sources, inside the fume hood when flammable liquids or solids are present
  • Do NOT remove the hood sash or panels unless absolutely necessary for setting up large equipment or glassware
  • NEVER put your head inside the working space of the fume hood
  • Minimize air turbulence at the face of the fume hood to prevent fumes circulating throughout the lab space
  • NEVER utilize/open a fume hood if the power is out, the fume hood has not passed annual inspection from EH&S personnel, or the rooftop blower fan has failed
  • Contact EH&S personnel at ehs@usd.edu if your fume hood is not functioning properly

Common Problems

  • Blocking the slots and baffles can obstruct air flow causing lower air flow within the working space
  • Leaving the baffle set to the closed position can cause reduced air flow within the space
  • An over filled fume hood will have greatly reduced air flow
  • In the case of shared ductwork, other users not complying with the listed safety tips can result in reduced air flow throughout the shared system
  • Open horizontally sliding glass panels in the front sash can result in user exposure when the sash is lifted and work is being performed in the hood

Questions about how a fume hood works or training requests can be submitted to ehs@usd.edu

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