The number of building materials covered in the national systems is not great, primarily because building materials are the subject of other evaluation processes that serve essentially the same purpose. But the numbers are growing, as many of these systems interpenetrate. The two categories of building materials that are most prominent in ecolabelling systems are paints and varnishes, and wood products. Wood certification is particularly important area, and I will devote special attention to it in the next section. There are three kinds of eco-labelling, set out by the International Standards Organization (ISO) in its document ISO 14020 Environmental Labels and Declarations General Principles. Type 1 is the most well-known, stamp of approval labels that include the major national systems, like Environmental Choice (the Ecologo system) in Canada) (Figure 10), Green Seal in the US (Figure 11), the Flower of European Union (Figure 4), and Nordic countries Swan. These systems are given for a product meeting a set of criteria determined by a third party evaluating group. Most often these groups employ process life-cycle analysis (LCA) as the means of evaluation.