Abstract |
This document describes a comprehensive laboratory study using specially designed controlled environment exposure chambers to assess the effects of gaseous air pollutants (sulfur dioxide, nitrogen dioxide, and ozone) on a variety of materials. Materials included weathering steel, galvanized steel, aluminum alloy, paints, drapery fabrics, white sidewall tire rubber, vinyl house siding, and marble. The exposure experiment was statistically designed using a two-level factorial arrangement to identify the environmental factors or combination of factors, or both, that cause materials damage. Over 200 different direct and synergistic effects were examined. The study revealed that only 22 of the possible effects were statistically significant at better than a 95 percent confidence level. Sulfur dioxide, relative humidity, and the interaction between them, were the main factors causing effects. A number of empirical functions were developed that relate materials effects to various factors causing the effects. An exceptionally good relationship was obtained for the corrosion of weathering steel. The lack of statistical significance that was found for the large majority of effects that were studied is equally as important as the significant effects. As a result a large number of material-pollutant combinations may be excluded from further detailed study. |