The Mosquito Net Trade-Off: Mesh Aperture Against Air Movement, and the Hole Size at Which a Net Stops Cooling the Sleeper It Protects

A mosquito net protects by exclusion and penalises by stillness: the finer the mesh, the less air moves under it, and in a hot room the loss of cooling is the price of the bite protection. This paper models air movement through netting as a stated function of its open-area fraction, for apertures from 0.4 to 2.0 mm against a stated thread diameter of 0.25 mm. At the 1.2 mm aperture that excludes the malaria mosquito, the open fraction is 0.685 and the air speed under the net falls to 0.567 of the unnetted value, with relative cooling at 0.711. The 0.6 mm mesh needed against sandflies cuts air speed to 0.352 and cooling to 0.534. The trade-off is quantified as a design table, and the implication — that in sandfly country a fan under the net is not a luxury but the compensating component — follows directly. This study is simulated, not measured.