Summary

The fume hood and other containment devices are part of the ventilation system and the user understanding of how these interact impacts the performance of the hoods in containing airborne contaminants.

  • How do the users best understand  the protection that fume hoods offer?
  • What constitutes improper use of this equipment and what are the consequences?
  • How can users identify when the ventilation system is not functioning properly?
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Discussion led by Dan Ghidoni,
Northeast Scientific Associates
Dan Ghidoni
Dan Ghidoni

Fume hood usability, by definition, involves the actions of the users with the fume hood, who may or may not have had input during the programming phase of the project. A significant amount of time and design decisions will have occurred before occupancy. Is the deliverable consistent with the intended use? The fume hood is only one component of a system. The building’s ventilation system, processes that are enclosed in ventilated equipment and user techniques all contribute to the safety and efficiency of the system.  This section will review the use factors affecting fume hood performance.

  • Review of types of engineering controls and their types of protection afforded.
  • Components of the containment system – engineering controls, air flow systems and controls, user procedures.
  • Things that can make the containment system fail.
  • Energy and Safety considerations for use and non-use times.
  • SOPs for operating equipment

Questions:

  1. Is the product delivered consistent with a risk assessment for the work being performed?
  2. Are there any equipment stored in the hood that was not anticipated, procedures being performed, or  occupancy changes?
  3. Have SOPs been established for the procedures using the equipment?
  4. Are flow / velocity alarms and sash stops in place and working?
  5. Are there ambient conditions that were not considered or that have changed?
  6. What limits should be place on the fume hood operation?
  7. Should “as used” testing be performed?
  8. What factors determine if a combination horizontal/vertical sash or vertical sash best fit the needs of the work being conducted?
  9. What is design opening for both configurations?
  10. Does the hood provide the researcher adequate visibility to equipment located up high on the monkey bars if this will be the set-up?  (sometimes folks just need to view up high and reach only occasionally).
  11. What utilities should be directly piped into the hood?
  12. What options are there for suppling electricity to the hood??
  13. What hood depth is best given the activities that normally take place in the hood?
  14. Will the hood be used to store chemicals or wastes awaiting pickup?
  15. Will researchers routinely need to reach to the back of the hood both at the work surface and higher?

Discussion by Small Group Participants

The group discussed a number of topics related to Usability Considerations:

  • The fundamental flow equation of Flowrate(Q) = Velocity * Area guides proper use of the hood
    • It is generally safer to reduce Area than Velocity unless Area is so restrictive that hood is routinely used in abuse conditions
    • Using diversity to allow 1 sash open while the other sash is closed (split sashes) is an important energy conservation strategy
    • As part of the design process, one should evaluate existing sash practices to determine system diversity
    • Reviewing Building Management System data to study sash diversity can be a fruitful avenue when one is available.
  • What Type of Hood Is Needed

    • How do we communicate diversity and other use restrictions to users?
    • Hood alarm (probably not common operating condition)
    • Training program
    • CFM display
    • Signage for the room
    • Number of hoods
    • Sash restriction mechanisms

airflow diagrams

  • Hood Management Communication Mechanisms

    • Getting users to close sash is key for both safety and sustainability
    • Automated sash closers
    • Communicate back to users on their practices and maybe how they compare to their peers (send emails)
    • Alarm hoods when they are open too long; this alarm should be clearly distinct from face velocity alarms
    • Recognition of good behavior through parties and training
    • Institutional consistency vs. innovation (should we standardize or customize based on hood use)?
    • How do we get feedback from users on sash height / sash type
    • Lab mock-up
    • Establish need in programming
    • End-users included in program decision making
    • EHS can help and need to be in programming decision making discussions
    • Users sometimes just ask for what they had
    • Use assessment / risk assessment step is required
    • A Hood Use SOP may be another communication tool
    • Process for getting effective feedback from users to determine best hood type and configuration
    • The Bottom Line: Tell us what you do; not what you need

flow patterns

  • What Can Go Wrong in an Operating Lab?

    • Users need to be trained on hood limitations / restrictions
    • How can they tell that the hood is on?
    • How does an automatic sash closure work?
    • What does hood alarm mean? What user actions does it indicate are needed?
    • What are the requirements for prior approval of specific processes in a specific hood?
    • What are the communication methods for inspection findings addressing issues such as clutter, sash height and functionality of the fume hood?
  • Training Program for Users

    • Criteria/Scope of Training
      • relate energy use of hood to home utility
      • training tied to funding
      • use smoke to show sash height containment limitations
      • Clear Signage on expected maximum sash height for use
      • what stays in the hood permanently?
      • sash stop
      • authorized usership
      • annual hood survey sign off by lab manager
      • training each semester
      • lab-specific training of users
    • How do we make such a program sustainable?
  • Other Factors to Consider

  • User specifications – front vision panel, side vision panel, lighting inside of hood, hood depth (architectural, ergo, lab automation)
  • The utilities required tend to be research dependent; examples include
    • cup sink
    • external controls preferred
    • quick disconnect vs. barbed for pressurized lines
    • provide adequate chemical storage in lab and organize regular clean-outs to minimize storage in hood
    • hazardous waste processing is ok in hood but hazardous waste storage is better provided somewhere else
  • Pharmaceutical industry is for profit vs. Education not for profit setting and have different levels of staff turnover and expected life cycles for people and projects; this will all influence the appropriate approach to fume hood design
  • A containment test (maybe smoke) that users can conduct themselves could be useful for certain use conditions; although some users prefer this testing be done by an EHS expert
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