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Note: EPA no longer updates this information, but it may be useful as a reference or resource.

Please see www.epa.gov/nsr/ for the latest information on EPA's New Source Review program.

September 21, 1987 Ambient Air Definition 6.33

EPA's policy on PSD increments and rooftops are contained in a memorandum issued by Joseph Cannon on June 11, 1984. This memorandum is clarifed here to contain clear guidance on placement of receptors on rooftops when modeling while defining rooftops as not ambient air when calculating increment consumption.

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