Keep your shelter cool and dry with AutoVent, the ultimate ventilation system for your shelter. Vent automatically opens and closes based upon the interior temperature. Reduce humidity and moisture buildup in your fabric garage or shelter. A bimetallic spring, which is heat sensitive, begins to open the vent at 74 degrees, fully opened at 104 degrees. When the interior temperature cools down, the vent begins to close up.*Quantity of 2 vents per box.