Capture velocity in LEV design is defined as what?

• A. The required air velocity at the capture hood to keep contaminants from escaping.
• B. The total air flow rate through the system.
• C. The static pressure in the duct.
• D. The velocity of air being exhausted to the atmosphere outside.

Answer: (A)

Capture velocity is the minimum airspeed at the capture hood required to pull contaminants into the hood and prevent their escape into the work area. It’s a design parameter that ensures the contaminant plume is drawn in at the source, depending on factors like the strength of the source, hood geometry and distance, and the properties of the contaminant. It’s not the total airflow through the system (that’s a volume-per-time measure), nor the static pressure in the duct, nor the velocity of air being exhausted to the atmosphere.