Airflow rating estimates are based on factory testing with standard filters installed at 120 VAC, 60 Hz with an air straightener and a traverse of readings taken with a computing vane-anemometer. Actual results may vary up to ten percent for various reasons, including motor and blower and HEPA filter tolerances. Factors such as filter loading, reduced voltage to the motor, and inlet and outlet ducting will reduce airflow. Use the ratings as a general guideline only.