On February 12, 2013, US EPA (EPA) proposed a rule that will require 36 states to eliminate an exemption to Clean Air Act (the Act) emission requirements for exceedances that occur during periods of startup, shutdown or malfunction (SSM). 78 Fed. Reg. 12459 (Feb. 22, 2013). The proposed rule (SSM Rule) will have a significant impact across numerous industries, including electric utilities, oil and gas operations, and industrial and manufacturing facilities where emission units such as boilers are used and permitted under the Act.