Local exhaust ventilation (LEV) versus general ventilation: which statement is accurate?

• A. Local exhaust ventilation captures contaminants at the source; general ventilation dilutes room air; both reduce exposure.
• B. Local exhaust ventilation captures contaminants at the source; general ventilation dilutes room air; only LEV reduces exposure.
• C. Local exhaust ventilation dilutes contaminants; general ventilation captures at the source.
• D. LEV is unrelated to exposure control; general ventilation reduces exposure.

Answer: (A)

LEV captures contaminants at the source, while general ventilation dilutes the room air. This distinction matters because capturing at the source prevents most of the contaminant from entering the worker’s breathing zone, often delivering a stronger and more targeted reduction in exposure, especially for high-concentration or localized emissions. General ventilation, on the other hand, increases overall air exchange in the space and mixes and dilutes contaminants in the room air, which reduces exposure more indirectly and depends on how well the air is exchanged and mixed.

The statement that accurately reflects this is that LEV captures at the source, general ventilation dilutes room air, and together they both contribute to reducing exposure. The other options misstate one or both mechanisms—for example, suggesting only LEV reduces exposure, or that LEV dilutes contaminants, or that LEV isn’t related to exposure control—none of which align with how these systems function in practice.