Similar source
Similar source means that equipment or collection of equipment that, by virtue of its structure, operability, type of emissions and volume and concentration of emissions, is substantially equivalent to the new affected source and employs control technology for control of emissions of hazardous air pollutants that is practical for use on the new affected source.
Source
40 CFR § 63.51
Scoping language
Terms used in 63.50 through 63.56 that are not defined in this section have the meaning given to them in the Act, or in subpart A of this part.