CFR > Title 40 - Protection of Environment > CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY > SUBCHAPTER C—AIR PROGRAMS (Parts 50–99) > PART 86—CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND ENGINES > SUBPART D—Emission Regulations for New Gasoline-Fueled and Diesel-Fueled Heavy-Duty Engines; Gaseous Exhaust Test Procedures (§86.301-79 to §86.348-79) > 86.318-79—Oxides of nitrogen analyzer specifications.

86.318-79—Oxides of nitrogen analyzer specifications.

(a) Oxides of nitrogen are to be measured with a chemiluminescense analyzer.
(1) The NOX sample must be heated per § 86.309(a) and § 86.310(a) up to the NO2 to NO converter.
(2) For high vacuum CL analyzers with heated capillary modules, supplying a heated sample to the capillary module is sufficient.
(3) The NO2 to NO convertor efficiency shall be at least 90 percent.
(4) The quench interference must be less than 3.0 percent as measured in § 86.327.
(b) Option. The oxides of nitrogen may be measured with an NDIR analyzer system that meets the following specifications:
(1) The system shall include an NO2 to NO converter, a water trap, and an NDIR analyzer in that order.
(2) The NO2 to NO converter shall obtain a sample directly from the heated sample line.
(3) The water trap shall meet the specifications in § 86.311(e).
(4) The NO NDIR analyzer shall be calibrated per § 86.330.
(5) The minimum water rejection ratio (maximum water interference) for the NO NDIR analyzer shall be 5,000:1 (see § 86.321 ).
(6) The minimum CO2 rejection ratio (maximum CO2 interference) for the NO NDIR analyzer shall be 30,000:1 (see § 86.322 ).