Air Basin

the air space within a city (settlement or village) or industrial plant area (the upper boundary of the air basin is usually regarded as passing over the tallest local building or structure).

The air basin is the source of air needed for the life of man, animals, and plants. It is also used for various technological processes, ventilation, heating, transport systems, and so on. Because of the rapid development of industry, the concentration of industry in limited areas of cities, and population growth, the air basin is continuously polluted by the emission from industrial plants and from ventilating and heating equipment and by disagreeable odors caused by the decomposition of organic wastes accompanying the life processes of man and animals. Industrial plants, heating and power plants, and vehicular transport create a special kind of pollution. The concentration of carbon monoxide from exhaust gases produced by automobiles on city roads is frequently above maximum permissible levels.

In some cases, under conditions of poor ventilation of the air basin, harmful substances may accumulate in the air layers near the ground, forming a toxic fog (smog) that may poison large numbers of people (a smog in 1952 in London killed about 4,000 persons and caused many respiratory dis-eases). The economic consequences of industrial emissions are loss of valuable raw material, destruction of vegetation, lowering of crop yields, and damage resulting from corrosion of various materials. Freeing the air basin from pollutants by natural means—that is, by wind and inversion air currents—depends on the climatic and meteorological conditions, the topography of the locality, and the degree of indus-trial concentration in the populated area. Such natural means frequently do not ensure the necessary cleansing of the atmosphere. Thus, sanitizing the air basin has become one of the most important tasks of modern town planning and the urban and communal economy.

In the USSR great importance is attached to the battle against air pollution. If the technological processes of an industrial plant involve the emission of harmful substances into the atmosphere, locating such a plant in a city is prohibited; plants that present health hazards are kept outside city limits. Gas is the main fuel used for heating because it produces the smallest amount of pollution when burned. With other types of fuel, use is made of centralized heat supply with efficient gas-purification devices installed in central boiler rooms or in heat and electric power plants. The level of pollution by vehicular transport is lowered by modernizing engines and operating them more efficiently and by using high-quality fuel. A radical solution to the problem of protecting the air basin against pollution by vehicular exhaust gases requires the complete electrification of municipal transport.

The air basin of industrial plants can be sanitized by introducing more modern equipment and technology, by using materials possessing little or no toxicity in technological processes, by making technological units and communications airtight, and by supplying industrial plants with apparatus and equipment for gas purification and recovery of emissions. Another means of reducing local pollution is to raise the height of smokestacks (to as high as 300 m) to carry off harmful emissions to great distances and disperse them more effectively at ground level. According to sanitary standards now in force in the USSR, industrial plants that release harmful substances (such as gas, smoke, soot, and dust) may not be built on the windward side of the nearest inhabited region. Planning all measures in the battle against air pollution (such as technological measures, purification apparatus and their effectiveness, height of emission of waste matter, extent of the health protection zone) proceeds from the idea that the content of harmful substances in the air of inhabited localities should not exceed the established limits of permissible concentrations. To satisfy these requirements, agencies of the state health inspectorate have set up special stations to monitor the condition of the air basin over cities.