Make a four-sided cardboard air hood with two open ends:
- Large end: 61 cm x 61 cm (2 ft x 2 ft) (standard floor tile size)
- Small end: 30.5 cm x 30.5 cm (1 ft x 1 ft)
- Place the hood with the large open end over a vented floor tile. Minimize air flow leakage by sealing seams on the hood, and by pressing the hood firmly against the floor.
- Hold the air flow meter at the small open end of the hood, in the center, to get a reading of the air velocity.
Convert the air velocity reading to the air flow rate.
The measurement in cubic feet per minute is:
flow rate (ft 3/min) = flow velocity (ft/min) x area (1 sq. ft on small open end of hood)