Fume Hood Usage Guide: Variable Air Volume Hoods ("Phoenix" System)

Per Cal-OSHA regulations, users of hoods must be trained on use of their fume hood. Attendance at one of the live or on-line lab safety orientations described below on the “UC Policy on Laboratory Safety Training” page satisfies that requirement. The information on this page should also be read by all hood users and is posted on campus hoods for easy reference.

  • Variable Air Volume (VAV) hoods — unlike a standard hood above — automatically adjust the face velocity to stay within recommended safe work levels (~ 100 ft./min). A VAV hood is easily distinguished by the gray control box on the hood – pictured below.
  • If the low-flow alarm engages, lower the sash until the alarm stops. DO NOT over-ride the safety alarm by permanently engaging the "Mute" or "Emergency" button (e.g., with tape). If your hood is consistently alarming call EH&S (805.893.4899).
  • Always work with the sash at or below the level of the red arrow sticker (below), because, if most bldg. sashes are raised, this will generate a hood alarm, and at your neighbor’s hood, due to the limited capacity of your building’s ventilation
  • A lowered sash protects you against airborne chemicals and incidents better than at sash full open.
  • The lower the sash, the greater the energy conservation – lower sash when not in use
  • Store only the minimum of equipment and chemicals in your hood because:
    • Excess materials block air flow into the slots at back of the hood. Permanent equipment should be raised on a stand to allow the air flow into the lower slot.
    • Most lab fires/explosions occur in hoods. Minimizing chemical volumes will reduce the chances of a small accident escalating into a large one.
  • Always work at least 6 inches inside the hood to maximize hood capture efficiency.


Phoenix Controls fume hoodfume hood indicating arrows