Reliable prediction of airflow through porous screens is essential to the selection of such devices, as well as to the manufacture of new screening materials. In the attainment of a satisfactory description of the airflow through porous screens, the principles of fluid mechanics provided a simple and accurate methodology for the identification of airflow characteristics. In order to evaluate the impact of screen usage on airflow reduction, the presence or absence of screens (when covering window or ventilator openings) was simulated. Finally, airflow characteristics of a number of porous screens with different uses were determined based on experiments. In view of these findings, some suggestions are made regarding screen design, aiming, for example, at the optimisation of ventilating systems management.