Laminar flow hoods and chemical fume hood

Common safety hoods in biological labs

Type Chemical fume hood Clean bench
(Horizontal laminar flow hood)		 Biosafety cabinet
(Vertical laminar flow hood)
Design Contain hazardous vapors and gases and exhaust them outside the building Forces air out from the back of the hood, across the work surface and toward the worker. Protects biological specimens from airborne contaminates. Particulate-free air is passed down from the top of the hood and across the work surface, and is captured before entering a worker's breathing zone. Protects both specimen and user.
Sterile No Yes Yes
Protect user Yes No Yes
Safe with hazardous gases and vapors Yes No. Air exhausts back into the work area. No. Air exhausts back into the work area.

Standard practices

  • Confirm that the hood is operational.
  • Maintain operations at least 6 inches inside the hood surface. Remind the user by marking the 6 inch position with a tape.
  • Lower sash to optimum height.
  • Don't block air flow with notebook, glove, paper, or pipet aid.
  • Keep head out of hood and above the openning.
  • Keep hood storage to an minimum.
  • Minimize foot traffic around the hood.
  • Use extreme caution when ignition sources inside a hood.

    In addition to those above, for sterile hoods:

  • Clean working surfaces with ethanol (70%) before and after use.
  • Don't bring in bacterial or fungi cultures.
  • Avoid bring in any media or equipment that has not been sterilized.
  • Sterilize working area with a short-wave UV light. Don't put you hand or face near the hood when the UV is on.
  • Turn on the hood 10-20 minutes before use.
For more information, visit http://www.niehs.nih.gov/odhsb/.