Glass, pollution effects

Two types of plastic panels [effective size, 0.6 x 1.0 m made from poly(vinyl chloride) resin] were used for testing the sheets in polluted areas. One is the open type (the sheets are exposed to air) and the other a windowed type. The open type can simulate realistic conditions. The windowed type has a Pyrex glass window that allows the UV light to reach the sheets. The roadside air was continuously pumped to the windowed panels at 15-60 1 min-1. This type was used for estimating the amount of air coming into contacted with the materials. The air purifying materials were attached to the panels using adhesive tape. 

The cast iron muffle was replaced by a fireclay brick muffle. The arch was made of carborundum which conducted heat well and withstood the effect of sulphuric acid. The outer brickwork was circular in shape and not rectangular as in the Mannheim furnace. Consequently, the surface area of the muffle was smaller so that the loss of heat due to radiation was reduced to a minimum. The interchangeable blades on the four arms of the stirring device, which revolved at a velocity of 1 to 2 r. p. m., were made of carborundum which resists to wear and does not pollute the product either with iron or chromium. This is of great importance when manufacturing sulphate for glass works. 

In 1953 the Public Health Service in cooperation with state and local departments in air-pollution control agencies set up air sampling stations in 17 communities. The Federal Air Pollution Research and Technical Assistance Act (Public Law 159, 84th Congress) became effective in June, 1955. The network expanded to become national in 1957, at which time about 110 urban and 51 non-urban stations in the 50 states, the District of Columbia, and the Commonwealth of Puerto Rico were operated on a continuing basis. Currently, the National Air Surveillance Network (NASN) includes some 270 stations (10% of which are non-urban) where particulate matter is collected on glass-fiber filters and TSP is deter-... 

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