This procedure for measuring air flow is specific to a raised floor environment. The air capture hood can be used to measure flow rate of an overhead air diffuser in an overhead air delivery environment, as long as the larger open end of the hood can cover the opening of the diffuser.
Handmade Air Capture Hood and Measurement Locations
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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.
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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)
If you need to calculate air flow rate in cubic meters per second (m 3/s), the conversion factor is 4.719 x 104.
For example, to obtain air flow rate in m 3/sec when measured air flow rate is X ft 3/min (CFM), multiply X ft 3/min by 4.719 x 104: X x 4.719 x 104.