Legal Question in Real Estate Law in Illinois

Well, without reviewing the documents it may be impossible to say. There are two kinds of "common elements". One kind is "common element" such as the roof, which protects the entire building. LIkewise, if the building has central heat and air, it is possible that the main ducts are also common elments. However, there are also "Limited Common Elements" which are common elements that serve one, or more, but not all the units. This normally includes your windows, entry door, etc, and could include ductwork that branches off the main ductwork and serves only your unit, or a few units through multiple branches, etc. The Declaration may make a difference between "Common Elements" and "Limited Common Elements" and often the Association will not be responsible for "Limited Common Elements". So once you know exactly what ducts are involved you should check the Declaration again in particular because you may be responsible for Limited Common Elements repair and maintenance even if the Association is responsible for true "Common Elements", but I've seen weird-er things, especially in smaller buildings.....