# Prevention of significant deterioration of air quality.
**CFR Correction**
In Title 40 of the Code of Federal Regulations, Parts 50 to 51, revised as of July 1, 2010, on page 265, in § 51.166, paragraph (b)(49)(vi) is added to read as follows:
§ 51.166
(b) * * *
(49) * * *
(vi) Particulate matter (PM) emissions, PM <sub>2.5</sub> emissions, and PM <sub>10</sub> emissions shall include gaseous emissions from a source or activity which condense to form particulate matter at ambient temperatures. On or after January 1, 2011 (or any earlier date established in the upcoming rulemaking codifying test methods), such condensable particulate matter shall be accounted for in applicability determinations and in establishing emissions limitations for PM, PM <sub>2.5</sub> and PM <sub>10</sub> in PSD permits. Compliance with emissions limitations for PM, PM <sub>2.5</sub> and PM <sub>10</sub> issued prior to this date shall not be based on condensable particular matter unless required by the terms and conditions of the permit or the applicable implementation plan. Applicability determinations made prior to this date without accounting for condensable particular matter shall not be considered in violation of this section unless the applicable implementation plan required condensable particular matter to be included.