Remove the old caulk with a putty knife. Brush the area around the seam between the dryer vent and the wall with a brush to remove leftover debris and provide a clean area for the new caulk to adhere.
Tighten all the screws securing the dryer vent to the wall with a Phillips-head screwdriver.
Insert a tube of silicone caulk into the caulking gun. Cut the tip of the tube at a 45-degree angle at the second line with a utility knife. Each tube has graduated cutting lines on the tip.
Apply a 1/4-inch bead of caulk around the perimeter of the dryer vent where it meets the house. Ensure there are no gaps between the caulk and the dryer vent. Allow the caulk to cure for 24 hours.