I'm about to purchase and install a new range hood since the old one is quite drafty and really in pretty bad shape, however, the vertical duct feeds into a horizontal duct that is also connected to a vertical dryer vent. I don't feel comfortable with this set up and am wondering if there shouldn't be two separate ducts. This property was built in the '60's and doesn't exactly seem to meet code. I recently cleaned the duct work and found no greasy buildup just a very large nest. The duct runs through a soffit to the outside and I don't believe there is room for another line. Can I continue to use the existing venting?