It is now recognized that the air transport of pollutants to distances outside of urban and local industrial areas must be considered for a number of environmental problems. Two general types of problems arise.. In the first, the concentration, deposition rate, or horizontal flux (flux through a vertical plane) is required for a specific time: a given hour, day, year, etc. For the resolution of such problems the weather data for that time must be used. In the second type, the average or typical concentration, deposition rate or horizontal flux is required. In this case, average climatic conditions should be used. The present handbook provides calculation procedures only for the second or the climatological properties of pollution after travel to distances of about 100 to 1.000 kilometres (km).