A method of measuring airflow from an HVAC outlet vent using a volume fill airflow measurement device having a LIDAR or Time-of-Flight (ToF) laser-ranging sensor to detect a filled state of a volume capture element or bag, comprising placing a frame having the bag sealably attached thereto over the vent to be measured, starting a timer, stopping the timer automatically in response to the LIDAR or Time-of-Flight (ToF) laser-ranging sensor measuring the distance to be within a predetermined range, and calculating the measured airflow based on the volume of the bag and the time for the airflow to fill the bag. The measured airflow is then displayed on the device display.