Thermal comfort is a fundamental issue for riders to take care of, especially in countries with very hot summer climate: the temptation of leaving out wearing the helmet turns out to be too strong if it is not sufficiently ventilated, with obvious consequences in terms of risk of injuries for the heat of the rider. For these reasons it is important for each helmet to be equipped with an efficient ventilation system, which should be able to remove the heat and sweat produced by the head of the rider. At the moment there is a total lack of fluid-dynamic guidelines for the design of such...