“Local Exhaust” means a ventilation device that is designed to capture room air at a specific location and exhaust it to the outside. The most common local exhaust ventilation system used in a laboratory is a chemical fume hood. Many of the common problems associated with fume hoods are cited in the ventilated enclosure portion of the checklist.
Examples of Items to be cited in this portion of the checklist rather than the ventilated enclosure portion of the the checklist are as follows:
- Use of “recirculating fume hoods.” Several manufacturers have come out with “green” fume hoods. They are designed with filters that are suppose to capture certain chemical vapors, leaving the exhaust air clean to re-circulate back into the lab, thereby dramatically decreasing energy consumption for heating/cooling. However, with rare exception, we do not allow use of filtering fume hoods. You can identify a filtering fume hood by the bank of filters at the top. Also be aware that “desk top” units are also made. If you find any style of a filtering enclosure, be sure to ask what it is being used for, the chemicals used in it and the quantities. Consult a Senior Specialist on appropriate follow-up action and citation.
- This checklist item may also be cited if chemicals or operations are conducted in the lab that should be in a fume hood and currently are not such as on the bench top or in a clean bench. When citing, distinguish whether a hood is present but not being used or one is not present at all.
Examples of situations that are NOT cited under this portion of the checklist include:
- The fume hood or associated flow monitors/alarms are obviously not working correctly. Examples of ways to identify this include odors escaping from the cabinet, non-responsive flow indicators/alarms when the sash is moved, and lack of or low flow of air movement into the cabinet. If this condition is noted, cite it under VEN04, Other ventilated cabinet safety concern.
- Misuse of a fume hood by a laboratory worker (e.g., cluttered, operated with sash too far open, etc.) is cited in VEN02, not in this portion of the checklist.