How do you determine whether a process requires a local exhaust ventilation system?

• A. If emissions are near-source and can be captured effectively at the source; evaluate concentration, capture velocity, and feasibility; if not, rely on general ventilation or PPE
• B. If the room has windows
• C. If the process uses water-based solvents
• D. If the operator requests

Answer: (A)

Local exhaust ventilation is considered when contaminants are produced at the source and can be drawn away before they contaminate the breathing zone. To decide if a process needs LEV, focus on whether the emissions originate near the process location and can be captured effectively with a hood or capture device at that point. If the contaminant can be pulled into the system by a properly designed hood with adequate capture velocity, and the resulting reduction in concentration at the worker’s breathing zone meets exposure limits, then installing LEV is the appropriate control. If the emissions cannot be captured at the source—because they disperse too quickly, spread beyond the hood’s reach, or the hood would be impractical or too costly—then relying on general ventilation or personal protective equipment may be more suitable. Other factors like whether the room has windows, the use of water-based solvents, or an operator’s request do not on their own determine the need for LEV; the decision hinges on the feasibility and effectiveness of capturing emissions at the source.