Passive ventilation in work helmets is a system of openings in the shell that allow for spontaneous air circulation. Warm and moist air from the head can escape, while cooler ambient air flows in. This process works on the principle of natural flow, known as convection, and is supported by user movement or wind. The result is increased thermal comfort and reduced sweating, which is particularly beneficial during physically demanding work or in hot environments. The design and placement of ventilation openings must always meet the requirements of the relevant safety standards. Some standards, for example for protection against electric shock, do not permit ventilation openings.