Class 1 Area (CIA)

Under the Clean Air Act, a Class I area is one in which visibility is protected more stringently than under the national ambient air quality standards; includes national parks, wilderness areas, monuments, and other areas of special national and cultural significance.

Source: U.S. Environmental Protection Agency. 2013. Terminology Service Terms of Environment. Accessed on 9 September 2013. Available at http://iaspub.epa.gov

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