What is LEV and how does it differ from general dilution ventilation?

• A. General dilution ventilation captures contaminants at the source.
• B. LEV dilutes room air.
• C. General dilution ventilation uses a dedicated duct to remove sources.
• D. Local Exhaust Ventilation captures contaminants at the source; general dilution ventilation mixes air to dilute contaminants.

Answer: (D)

Local Exhaust Ventilation (LEV) is designed to capture contaminants right at the source, using a hood or capture device placed close to where the emission occurs. The contaminated air is then exhausted away (often through dedicated ductwork, sometimes with filtration) before it can spread into the breathing zone. General dilution ventilation, by contrast, brings in outdoor air and mixes it with indoor air to dilute contaminants throughout the space, relying on air changes per hour rather than capturing emissions at their origin. This makes LEV especially effective for localized, high-concentration sources, while dilution ventilation is more appropriate for lower concentrations or widespread, diffuse emissions.