An air duct vent can sometimes develop a problem which causes them to leak. Sometimes this can mean that dust, cold air and even poisonous gases can be released into your home. If your air duct vent has developed a leak, then the quickest fix is to re-seal it, this can be done in under an hour by even a beginner in home improvement.
Step 1 - Locate the Leak
You should be able to locate your leak by looking at the air duct vent in each room. Use a stepladder to examine each vent as closely as possible, if they are above your eye-line. Vents with a problem will usually show stains in that area. You may also note gaps in the insulation, cracks in the old seals, and dirt around the problem.
Step 2 - Seal the Duct
You can use duct tape to provide a good seal for your ducts. You should also add a layer of duct mastic, which is a paste which seals the space around ducts. Place it around the edge of duct openings, and also along joints, and any corners or edges of covers which are around the duct. Seal any seams by adding the mastic and then applying some duct tape over the top.