• Supply of as much fresh air as possible below deck, spray water must be sufficiently drained.
• Fans with rotatable cowl vents can be used as extractor and exhaust ventilators.
• In case of very bad weather conditions, they must be closable.
• If possible, a simple design without wearing parts.
The performance of a cowl vent depends on its cross-section and on the prevailing wind conditions. Flush deck and mushroom fans do not have the same ventilation effect as a cowl, but may be added additionally.
As a guideline for a suitable number of fans, there can be at least two for larger cabins (e.g. the salon) and one for smaller rooms. It is important to ensure that different types of fans complement each other in their mode of action, i.e. an extractor and exhaust fan. Fans should not be installed too close to the sides of the deck due to water swells.