Managing Fume Hoods: The Technical and Social Challenges

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Managing Fume Hoods The Technical and Social
Challenges
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History of Fume Hoods

• Technical History
• Open windows (Williams)
• Laboratory furniture (Cook)
• Building equipment (Given)
• Integrated laboratory ventilation systems (HSRF)
• UVMs Oversight History
• 1980s Its the labs problem
• 1990s Annual certification of face velocity
• 2000s ASHRAE testing at installation

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The 21st Century Challenge Balancing Safety,
Energy Use and Adaptability

• Stakeholders
• Project Managers (Design Plan)
• Laboratory Workers (Users Do)
• Campus Facility Managers (Maintenance Act)
• Upper Management (Energy Budget Check)

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Counting Fume Hoods at UVM

• There are about 400 fume hoods at UVM
• We are adding 10 more in the next two years
• Air used by hood
• 600 cfm
• 100 fresh air
• Office space 116 cfm per person, 20-50 fresah
  air

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Cost Estimates

• Financial costs
• Using commercial cfm costs 1300/hood/year
• Analogy to electricity costs 3000/hood/year
• Lawrence Berkeley National Laboratory DOE
  project 5000/hood/year
• Leads to the National Question what can we do to
  control the costs (both dollar and ghg) of fume
  hoods

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The Technical ApproachCAV and VAV

• CAV (Constant Air Velocity) hoods pull the same
  amount of air whenever the hood is on
• Some CAV hoods have high speed / low speed
  settings
• Simple to understand and maintain
• VAV (Variable Air Velocity) hoods change the
  motor speed depending on the height of the sash
• Requires sash height sensor and computer controls
  of both supply and exhaust fans
• Significant energy savings
• Harder to understand and maintain

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Lab Air Flow

• Old School minimum 10-12 ACH (air changes per
  hour) occupied
• New School varies
• Computational Flow Dynamics Modeling
• Active Chemical Monitoring
• Some have gone to 4-8 ACH occupied or lower based
  on these

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Low Flow Hoods

• Aerodynamic design allows them to be effective at
  lower face velocity
• Pass ASHRAE, EU tests

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Occupancy Sensors

• Set back when unoccupied
• Timers
• Light switch
• Sash position
• Occupancy Sensors
• Higher first costs, quick payback
• Higher maintenance than Continuous air

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Automatic Sash Closers

• Close sash when no one is using the hood
• Princeton Step Pad Study time in front of hood
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• Technology has improved
• Issues
• Auto close vs. open
• Timing
• Proximity vs. motion