The total thickness of the wall covering is approximately 0.055 inch to 0.070 inch (1.4 mm to 1.8 mm). During processing, the blowing agent decomposes, causing this layer to expand by forming closed cells. The expanded base coat layer is a homogeneous vinyl layer that contains a blowing agent. Wall covering consisting of a woven textile backing, an expanded vinyl base coat layer and a non-expanded vinyl skin coat. The following words and terms shall, for the purposes of this chapter and as used elsewhere in this code, have the meanings shown herein.