Multiply corrected velocity times area to get quantity of airflow. Barometric pressure 24 in. Therefore the correction factor for this example is 1.12. The average velocity in the 28 inches x 22 inches duct in the building in Cheyenne, Wyoming, is 1350 fpm. Find the cubic feet per minute.
Anemometers require a correction or flow factor for each outlet to convert velocity readings to cfm.
They are also good for low flow conditions where vane anemometers can't be used. Capture Hoods A capture hood may also be used to measure sidewalls and ceiling diffusers. However, if a capture hood reading is in question, and a correction factor seems indicated, because of extraordinarily high or low velocities or an unusual use of the capture hood, take a traverse of the duct and determine a correction factor. In addition to a field-measured correction factor for air devices, check the capture hood for a manufacturer's calibration or correction factor. The new technology is to use a device that allows the direct input of the variables that would change the reading from standard conditions.