Part 7 Title 40 CFR, Maintenance of Diesel Powered Equipment, states that--

g.	Undiluted exhaust emissions of diesel engines in diesel-powered equipment approved under part 36 and heavy-duty non-permissible diesel-powered equipment as defined in 75.1908(a) in use in underground coal mines shall be tested and evaluated weekly by a person who is trained to perform this task.  The mine operator shall develop and implement written standard operating procedures for such testing and evaluation that specify the following:
	1.	The method of achieving a repeatable loaded engine operating condition for each type of equipment
	2.	Sampling and analytical methods (including calibration of instrumentation) that are capable of accurately detecting carbon monoxide in the expected concentrations
	3.	The method of evaluation and interpretation of the results
	4.	The concentration or change in concentration of carbon monoxide that will indicate a change in engine performance. Carbon monoxide concentration shall not exceed 2500 parts per million; and
	5.	The maintenance of records necessary to track engine performance
h.	Record-keeping.  Records required by paragraphs (f) (2) and (g) (5) shall be--
	1.	The method of achieving a repeatable loaded engine operating condition for each type of equipment
	2.	Sampling and analytical methods (including calibration of instrumentation) that are capable of accurately detecting carbon monoxide in the expected concentrations
	3.	The method of evaluation and interpretation of the results
	4.	The concentration or change in concentration of carbon monoxide that will indicate a change in engine performance. Carbon monoxide concentration shall not exceed 2500 parts per million; and
	5.	The maintenance of records necessary to track engine performance

Diesel-powered equipment must be maintained in accordance with this regulation as of November 25, 1997.