Environmental engineers have modified the technique of using fiber filter cemented to a petri dish by using sodium carbonate rather than lead peroxide to measure sulfur gases. This method also indicates the concentration of other gases, including nitrogen oxides and chlorides. Engineers have measured relative levels of gaseous fluoride air pollution using larger filters, e.g., 3-in diameter, dipped in sodium carbonate, and placed in shelters to protect them from the rain. With all these static methods, the accuracy is low, and the data cannot be converted directly into ambient air concentrations. They do, however, provide a low-cost indicator of levels of pollution in an area.
Environmental engineers have evaluated the corrosive nature of the atmosphere using standardized steel exposure plates for extended periods to measure the corrosion rate. This method provides a gross indication of the corrosive nature of the atmosphere. As with other static samplers, the results are not directly related to the concentration of air pollutants.
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