40 CFR § 86.1509 - Exhaust gas sampling system.
(a) The exhaust gas sampling system shall transport the exhaust sample from the engine or vehicle to the analysis system in such a manner as to maintain the integrity of the sample constituents that are to be analyzed.
(b) The sample system shall supply a dry sample (i.e., water removed) to the analysis system.
(c) A CVS sampling system with bag or continuous analysis as specified in 40 CFR part 1065 is permitted as applicable. The inclusion of an additional raw carbon dioxide (CO2) analyzer as specified in 40 CFR part 1065 is required if the CVS system is used, in order to accurately determine the CVS dilution factor. The heated sample line specified in 40 CFR part 1065 for raw emission requirements is not required for the raw (CO2) measurement.
(d) A raw exhaust sampling system as specified in 40 CFR part 1065 is permitted.