One of the key factors when designing an applicable and realistic dust test method is the type of dust to be used. For this reason adequate knowledge of dust properties is necessary. The impact of dust was underestimated for a long time. In the last years an increasing interest in the environmental factor of dust became of essential significance. Due to the influence on health the impact of dust within the climate and global ecological system is of particular importance. Methods of measurement allow characterizing dust and its fluctuation with highest accuracy, leading to the knowledge that larger particles (larger than 100 m) including room dust, coarse sand and soot aggregates fall out quickly. Medium-size particles in the range 1 m to 100 m settle out slowly (e.g. pollen, fly ash, coal dust, fine sand). Small particles (less than 1 m, e.g. soot and tobacco smoke) fall even more slowly. In a quiet atmosphere it takes days up to years for dust to settle out and it can be carried over distances of more than 1000 km, but it can be washed out by rain very quickly [3].