Local Exhaust Ventilation (LEV)

Because there are many types of LEV systems, it is not possible to provide guidance on how to best use all of them.  Below are some general instructions on using LEV and specific information for the most common types used on campus.

General Tips

• For self-contained units that use a filter (i.e. ductless fume hoods and down draft tables) ensure it has the correct filter for the chemical you are working with.  A HEPA filter will only provide protection for particles, vapors and gases will pass right through.
• Ensure there is air flow before starting work. Clogged duct work and filters can drastically reduce the amount of air flow in a system.
• Read any manuals that come with the system so that you are aware of its intended use and any limitations it has.

Ductless Fume Hoods/ Enclosures

• Follow all the guidelines for ducted fume hoods. These can be found in the  ICON training course, Chemical Fume Hoods - W485CM, and in the UI Chemical Hygiene Plan, Section 9.0 Facility and Equipment Safety.
• Do not use Bunsen burners or hot plates in the units unless the manual states that is acceptable. The heat from these instruments can damage the filters if the hood is not designed for it.
• If you are using one that has carbon filters for controlling exposures to fume and vapors, consult this Ductless Fume Hood Use Guide. 

Snorkels 

• For procedures where the chemicals are being heated, the snorkel can be placed above the operation like a mini canopy hood.
• For low velocity contaminant release (i.e. general chemical mixing and welding), position the snorkel at 30-45 degrees off horizontal in front of the employee to maximize the capture zone.  The capture distance listed on the LEV test sticker is how far the snorkel should be placed from the source.
• For higher velocity contaminants (i.e. sanding and grinding), place the snorkel so the particles are thrown into the snorkel. The snorkel may need to be moved closer than the listed capture distance.

Canopy Hoods

• Canopy Hoods should only be used with hot processes as they depend on the lift from the hot air to carry the contaminates into the hood.
• Canopy hoods should not be used if the employee needs to lean over the work area.
• Adding sides to the canopy hood can help increase its efficiency and reduce the impact of cross drafts.

Downdraft Table

• Downdraft tables are best for processes that generate larger particles and can be ineffective at capturing contaminants from hot processes.
• Keep the surface as free of other tools and materials as possible as this can restrict the airflow making the table ineffective.
• Work as close to the bench top as possible to maximize the collection effectiveness.

Paint Booth

• Always spray straight into the fume hood. If multiple sides of a piece need to be painted rotate the piece so the paint can continue to be sprayed straight in.