[Code of Federal Regulations]
[Title 40, Volume 18]
[Revised as of July 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR92.112]

[Page 431-432]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 92--CONTROL OF AIR POLLUTION FROM LOCOMOTIVES AND LOCOMOTIVE ENGINES--
Table of Contents
 
                       Subpart B--Test Procedures
 
Sec. 92.112  Analytical gases.

    (a) Gases for the CO and CO2 analyzers shall be single 
blends of CO and CO2, respectively, using zero grade nitrogen 
as the diluent.
    (b) Gases for the hydrocarbon analyzer shall be single blends of 
propane using zero grade air as the diluent.
    (c) Gases for the methane analyzer shall be single blends of methane 
using air as the diluent.
    (d) Gases for the NOX analyzer shall be single blends of 
NO named as NOX with a maximum NO2 concentration 
of 5 percent of the nominal value using zero grade nitrogen as the 
diluent.
    (e) Fuel for the HFID (or FID, as applicable) and the methane 
analyzer shall be a blend of 402 percent hydrogen with the 
balance being helium. The mixture shall contain less than 1 ppm 
equivalent carbon response; 98 to 100 percent hydrogen fuel may be used 
with advance approval of the Administrator.
    (f) Hydrocarbon analyzer burner air. The concentration of oxygen 
must be within 1 mole percent of the oxygen concentration of the burner 
air used in the latest oxygen interference check (%O2I). If 
the difference in oxygen concentration is greater than 1 mole percent, 
then the oxygen interference must be checked and the analyzer adjusted 
if necessary, to meet the %O2I requirements. The burner air 
must contain less than 2 ppmC hydrocarbon.
    (g) The allowable zero gas (air or nitrogen) impurity concentrations 
shall not exceed 1 ppm equivalent carbon response, 1 ppm carbon 
monoxide, 0.04 percent (400 ppm) carbon dioxide and 0.1 ppm nitric 
oxide.
    (h)(1) ``Zero-grade air'' includes artificial ``air'' consisting of 
a blend of nitrogen and oxygen with oxygen concentrations between 18 and 
21 mole percent.
    (2) Calibration gases shall be accurate to within 1 
percent of NIST gas standards, or other gas standards which have been 
approved by the Administrator.
    (3) Span gases shall be accurate to within 2 percent of 
NIST gas standards, or other gas standards which have been approved by 
the Administrator.
    (i) Oxygen interference check gases shall contain propane at a 
concentration greater than 50 percent of range. The concentration value 
shall be determined to calibration gas tolerances by chromatographic 
analysis of total hydrocarbons plus impurities or by dynamic blending. 
Nitrogen shall be the predominant diluent with the balance being oxygen. 
Oxygen concentration in the diluent shall be between 20 and 22 percent.
    (j) The use of precision blending devices (gas dividers) to obtain 
the required calibration gas concentrations is acceptable, provided that 
the blended gases are accurate to within 1.5 percent of NIST 
gas standards, or other gas standards which have been approved by the 
Administrator. This accuracy implies that primary gases used

[[Page 432]]

for blending must be ``named'' to an accuracy of at least 1 
percent, traceable to NIST or other approved gas standards.