The passive flow hood (at left) and powered flow hood (right) shown here side by side can be used to measure air flow through outside air intakes, exhaust fans air conditioner supply
Using An Alnor Ebt721 Balometer For Air Flow Measurements
ALNOR Balometer HVAC Flow Capture Hood Jr Velometer 634-593-132 for sale online | eBay
TSI Alnor 801201 Hood and Frame Kit 2 ft x 4 ft - FLW, Inc.