Use of air barriers to prevent entrance of house flies.

Laboratory tests indicate that 8-20% of the house flies Musca domestica L. released are capable of penetrating an air barrier when the average air velocity is from 1536 to 2200 ft per minute (ft/min). A 92% exclusion was obtained when the air was discharged into the release room at a 15° angle and a velocity of 1793 ft/min. In general, effectiveness was similar with air velocities in the range of 1500-2200 ft/min and a discharge opening of 1, 3, or 5 inches. Field tests with an air-barrier fan showed that a velocity of 1736 ft/min prevented 80% of the house flies from entering. The use of velocities higher than 1,500 ft/min in food-handling establishments does not appear feasible from the standpoint of public acceptance.