The Face Velocity Method is used to measure what, and under which survey conditions?

The Face Velocity Method is used to measure what, and under which survey conditions?

• A. Measures face velocity at the hood
• B. Determines duct static pressure using a pitot tube
• C. Measures the velocity at the face of the hood, obtained by Q=AV, used in baseline or routine survey, not with initial survey
• D. Is used only for initial survey

Answer: (C)

Face velocity is the air speed right at the opening of a containment hood. The Face Velocity Method uses the relationship V = Q/A, where Q is the volumetric flow rate through the hood and A is the hood’s opening area, to determine the velocity at the hood face. This measurement is typically performed during baseline or routine surveys to verify that the hood maintains the required capture velocity during normal operation. It is not used for the initial survey, which relies on other methods to assess containment performance. Using a pitot tube to measure duct static pressure pertains to a different set of measurements and is not what this method assesses, and the idea that it’s used only for an initial survey is incorrect.

Face velocity is the air speed right at the opening of a containment hood. The Face Velocity Method uses the relationship V = Q/A, where Q is the volumetric flow rate through the hood and A is the hood’s opening area, to determine the velocity at the hood face. This measurement is typically performed during baseline or routine surveys to verify that the hood maintains the required capture velocity during normal operation. It is not used for the initial survey, which relies on other methods to assess containment performance. Using a pitot tube to measure duct static pressure pertains to a different set of measurements and is not what this method assesses, and the idea that it’s used only for an initial survey is incorrect.