Air permeability is a very important property influencing the performance of clothing comfort and technical textiles particularly in applications for protective products, including airbags, parachutes, and tents. Several analytical models for predicting air permeability have been made by considering porosity and pore diameter or porous area. However, the connection between fabric structure and air permeability with analytical models has not been well reported as yet. In this work, the diameter of cotton yarn was predicted by considering yarn count, twist, and packing density. Subsequently, the pore area and equivalent pore diameter of fabric were predicted after finding the warp and the weft densities of fabric. The predicted values had very good agreement with the experimental results in yarn diameter and other structural parameters of fabric. The air permeability of fabrics was measured and several well-known analytical models for predicting air permeability were compared. The results revealed that the Hagen–Poiseuille equation had much better prediction than other models and also had good agreement with the experimental results, especially when it was applied for tight fabrics at low pressure drop (≤60 Pa). The Hagen–Poiseuille equation could be improved by considering the Reynolds number, interfiber interstices, and the deformation of pores under higher pressure drop.
