Chem Hoods21st Century


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Chem Hoods21st Century

  1. 1. Sponsored by: American Chemical Society, Campus Consortium for  Division of Chemical Health & Safety Environmental Excellence
  2. 2. Ralph Stuart, CIH Environmental Safety Manager University of Vermont
  3. 3. • Design History • Open windows • Laboratory furniture • Pre-installed building equipment • Integrated laboratory ventilation systems
  4. 4. • In the 1980’s, the rule of thumb was that face velocities between 100 and 150 fpm were the best indication of “safety” • In the 1990’s, studies indicated that measuring face velocity was not enough, so tests using tracer gas were developed (ASHRAE 110 testing)
  5. 5. • 1980’s: “It’s the labs’ problem” • 1990’s: OSHA Lab Standard led to Environmental Safety certification of face velocity • Around this time, maintenance workers began to deal with hoods more systematically • Upward exhaust • Managing combined exhausts • In the 2000’s, ASHRAE tracer gas testing of containment “as installed” has become common
  6. 6. • From an energy point of view, hoods are the equivalent of a open window year round. • Energy considerations focus on the volume of air moved (air changes per hour) rather than its speed. • Traditionally, facility managers have erred on the safety side by over-ventilating laboratories • As the number of hoods has proliferated and fuel costs have risen, energy concerns have made assessing “hood performance” more complicated • Many ways of reducing the air volume exhausted have been proposed. • HVAC engineers now speak of “high performance” hoods with regard to energy use, but (hopefully) without a change in safety performance
  7. 7. • Laboratory buildings represent 15-20% of campus floor space, but consume around 40% of the campus’ energy • Studies have found that only about 20% of the installed hoods are used and someone is at used hoods only 20% of that time. • These observations lead to questions: • Are chemical hoods and laboratory ventilation are the best approach to laboratory safety? • Do our laboratories really need to be open 24-7 with full HVAC services? • Can we make assumptions about chemical risks in the lab?
  8. 8. • Fume hoods were developed to control flammable chemicals to control fires • The chief reason for the popularity of fume hoods is that it is a very adaptable design • The design has been re-purposed to serve as containment devices to protect human health from unclear potential risks using the ALARA approach • However, user behavior can trump design: • To achieve ALARA, it’s important that lab workers follow good hood work practices • Proper use of a chemical hood requires a risk assessment of the chemicals used so that the protection strategy is clear.
  9. 9. • ANSI Standard Z9.5-2003 • Outlines a Laboratory Ventilation Management Program with appointment of “responsible person” to oversee laboratory ventilation systems. • The general approach of the standard follows the “management system” approach. • This standard is referenced by many designers as well as in the Labs-21 proposed LEED criteria
  10. 10. • Process Analysis • Plan: Design • Do: Use • Check: Cost of operation • Act: System maintenance • Stakeholders • Laboratory Designers • Laboratory Workers • Upper administration and sustainability office • Facility Operations and Maintenance
  11. 11. • Laboratory Designers: What hoods should we buy? • Laboratory Workers: When should I use hoods? • Upper Management and Sustainability Office: Do hoods have to cost so much? • Campus Facility Managers: How much money do I need to operate and maintain hoods?
  12. 12. • External standards • Fire Protection: NFPA 45 • Containment: ASHRAE 110 • Energy Use: LEED and Labs-21 • Possible design criteria • Hoods must pass ASHRAE As Installed (0.1 ppm leakage at 4 liters/minute); passing face velocity must be established at installation • Energy conservation in design: basis of design documentmust describe design features (occupancy sensors, sash sensors etc.) and be translated to users
  13. 13. • 40% workforce turnover every 2 years • User signals and training: 1. Tell tales to determine if the hood is on 2. Warning signs in first 6 inches of hood 3. Safe Operating Height sticker 4. Close the sash reminder poster
  14. 14. • GHG impact: one chemical hood is the energy equivalent of about 3 houses • Each hood represents about $5000 to $10,000/year in energy costs • Laboratory buildings represent at least 35% of a research campus’s energy use
  15. 15. • Hood maintenance needs: • Face velocity check • Calibration of alarms and controls • Preventive maintenance of fans and hood components • Repairs • System adjustments during renovations • Re-commissioning and retro-commissioning for proper hood performance, with regard to both safety and energy
  16. 16. Robin M. Izzo Associate Director Princeton University Environmental Health and Safety
  17. 17. • Effective at lower face velocity • Pass ASHRAE, EU tests • Problems – design and use • Higher first costs • Larger footprint
  18. 18. • Close sash when no one is using the hood • Princeton Step Pad Study: time in front of hood = 5% • Technology has improved • Issues: • Auto close vs. open • Timing • Proximity vs. motion
  19. 19. • Variable Air Volume is almost the standard • Set back when unoccupied • Timers • Light switch • Sash position • Occupancy Sensors • Higher first costs, quick payback • Higher maintenance than Continuous air
  20. 20. • Especially useful with VAV systems • Maximum number of hoods in use with sash open at the same time • Significant first cost savings • Be realistic!! • Always design n+1
  21. 21. • Teaching lab solution • Three settings: • On • Off • Set-up • Lab instructor controls with key • Princeton: per week • on 15 hours, off 153 hours
  22. 22. • Not really fume hoods • Limitations • Filters • Flow • Code requirements • Maintenance • Limited application • Gaining popularity • Emerging technologies
  23. 23. • 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
  24. 24. • Know the applications • Know the building • Maintenance is key • Still need a minimum airflow in the lab • Limiting factor - USERS
  25. 25. • Very few regulations specifically about fume hoods • Many guidance documents • International Mechanical Code 510 • Adopted by many municipalities • 2006 version includes exemptions for labs • Your mileage may vary
  26. 26. • Defines Hazardous Exhaust • Precludes manifolding • Requires sprinklering within the duct • Requires detection within the duct • MOST LAB APPLICATIONS fit under the laboratory exemption • Documentation is the key
  27. 27. • Work with your design team • Talk to the users • Understand the applications • Look beyond those applications • Try the options on for size • Installation, visits, meetings • There is no panacea – just because it works for Princeton…
  28. 28. Sponsored by: American Chemical Society, Campus Consortium for  Division of Chemical Health & Safety Environmental Excellence