To be effective, boat ventilation must do more than just circulate air - it must also equalize the humidity inside and outside your boat. For comfort aboard, every boat should have exhaust vents in the head and galley, and intake ventilation in the main cabin to maintain a steady flow of air. Active systems, like solar and 12vDC vents, push air mechanically with fan blades.
Passive systems use wind and air currents, but no moving parts.
They include cowl vents, clamshells, louvers, and vent plates. Passive Vents, like Nicro's Lo-Vents, PVC cowls, and clamshells, are inexpensive systems that can be installed for either intake or exhaust. They're a great choice for small areas like chain lockers or lazarettes. Louvered Vents, the most basic and least expensive vents, are available in stainless steel or ABS plastic. These are used for ventilating fuel lockers, bilges, deck boxes, lazarettes, or behind electronics.