Thank you for your question on the model 103023 range hood. First make sure that the unit is installed with 3-1/4” x 10” rectangular duct work. This can also be converted to 6” or 7” round duct work. Make sure that everything is attached tightly inside the unit housing. You also want to check and make sure there are no obstructions inside the duct work. If all of these things check out, please contact our Technical Service Department at 800-637-1453 and we can assist you further.