The following units are exempt from this division, except as specified in §§117.240(f), 117.245(f)(4) and (9), and 117.252 of this title (relating to Continuous Demonstration of Compliance; Notification, Recordkeeping, and Reporting Requirements; and Control Plan Procedures for Reasonably Available Control Technology (RACT)):(1) stationary gas turbines and gas-fired lean-burn stationary reciprocating internal combustion engines that are used as follows:(A) in research and testing of the unit;(B) for purposes of performance verification and testing of the unit;(C) solely to power other gas turbines or engines during startups;(D) exclusively in emergency situations, except that operation for testing or maintenance purposes of the gas turbine or engine is allowed for up to 100 hours per year, based on a rolling 12-month basis; or(E) in response to and during the existence of any officially declared disaster or state of emergency;(2) gas-fired lean-burn stationary reciprocating internal combustion engines with a horsepower (hp) rating less than 50 hp;(3) stationary gas turbines with a maximum rated capacity less than 10.0 million British thermal units per hour; and(4) units located at a major source that is subject to Subchapter C, Division 2 of this chapter (related to Bexar County Ozone Nonattainment Area Utility Electric Generation Sources).