Ambient Air Definition/Interpretations

Date	Title	EPA Office	Author	Issues Addressed
12/02/2019	Revised Policy on Exclusions from "Ambient Air"	Administrator	Wheeler, Andrew	Addresses what atmosphere may be eligible for exclusion from the scope of “ambient air.”
05/23/1977	Applicability of PSD Increments Over Company Property	OAQPS	Barber, Walter	Whether PSD increments apply over property owned by a new source if the general public is effectively precluded from access to that property.
12/19/1980	Dec. 19, 1980 Ambient Air Letter	Administrator	Costle, Douglas	Letter explaining when the exemption from the definition “ambient air” is applicable.
09/11/2007	Determining the Ambient Air Boundary for Potential Permit Application in Support of Alaska Industrial Development and Export Authority's Restart of Healy Clean Coal Project	Region 10	Helm, Nancy	Determination of ambient air boundary for leased property for 3 scenarios.
03/01/1985	Applicability Determinations for Columbian Chemical Company	CPDD	Tyler, Darryl	Whether reductions in H2S can be considered in calculating SO2 concentrations given that H2S converts to SO2 in the ambient air surrounding the facility and whether replacement of the existing boiler with a new larger boiler will be subject to PSD. This memorandum also addresses the definition of ambient air when the facility intends to restrict general public access to this land.
10/17/1989	Ambient Air	OAQPS	Bauman, Robert	Discusses proposal that PSD modeling for Mitsubishi discount the contribution of a background source to the predicted concerning in a number of ways.
06/22/2007	Interpretation of "Ambient Air" in Situations Involving Leased Land Under the Regulations for Prevention of Significant Deterioration (PSD)	OAQPS	Page, Stephen	Responds to various inquiries about the interpretation of the definition of “ambient” air as it pertains to situations involving leased land under the PSD regulations.
04/13/1992	Request for Further Clarification on EPA's Definition of "Ambient Air"	OAQPS	Seitz, John	Provides further clarifications regarding the definition of ambient air as it relates to air intakes of mechanically ventilated buildings.
08/01/2000	Interpretation of Ambient Air	Region 7	Toensing, Don	Interprets ambient air for a source that has purchased adjacent agricultural land with a three-strand barb-wire fence enclosing the land and where the source will post “no trespassing” signs around the perimeter and at all entrances, will gate and lock all entrances, and will enter into a “License Agreement” with a farmer.
01/09/2007	Ambient Air for Offshore Liquified Natural Gas Broadwater Project	Region 2	Riva, Stephen	Whether emissions from a docked liquefied natural gas (LNG) carrier be assessed inside the ambient air boundary since the boundary only pertains to Broadwater itself and whether it is appropriate to use the Coast Guard’s proposed safety and security zone as a surrogate for defining an ambient boundary around the proposed LNG facility.
07/27/1987	Ambient Air Issue from New Jersey Department of Environmental Protection	OAQPS	Helms, G. Tom	Determination of ambient air applicability in the vicinity of a proposed cogeneration unit which will build and operate the plant on property leased through a long-term lease.
09/21/1987	Ambient Air Definition	OAQPS	Helms, G. Tom	Regards need for clarification of EPA policy on PSD increment consumption on rooftops.

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