[Code of Federal Regulations]
[Title 40, Volume 17]
[Revised as of July 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR86.123-78]

[Page 489-491]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 86_CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND 
ENGINES--Table of Contents
 
 Subpart B_Emission Regulations for 1977 and Later Model Year New Light-
 
Sec. 86.123-78  Oxides of nitrogen analyzer calibration.

    The chemiluminescent oxides of nitrogen analyzer shall receive the 
following initial and periodic calibration.
    (a) Prior to introduction into service and at least monthly 
thereafter the chemiluminescent oxides of nitrogen analyzer must be 
checked for NO2 to NO converter efficiency. Figure B78-9 is a 
reference for paragraphs (a) (1) through (11) of this section.

[[Page 490]]

    (1) Follow the manufacturer's instructions for instrument startup 
and operation. Adjust the analyzer to optimize performance.
    (2) Zero the oxides of nitrogen analyzer with zero-grade air or 
zero-grade nitrogen.
    (3) Connect the outlet of the NOX generator to the sample 
inlet of the oxides of nitrogen analyzer which has been set to the most 
common operating range.
    (4) Introduce into the NOX generator analyzer-system an 
NO in nitrogen (N2) mixture with an NO concentration equal to 
approximately 80 percent of the most common operating range. The 
NO2 content of the gas mixture shall be less than 5 percent 
of the NO concentration.
    (5) With the oxides of nitrogen analyzer in the NO mode, record the 
concentration of NO indicated by the analyzer.
[GRAPHIC] [TIFF OMITTED] TR06OC93.160


[[Page 491]]


    (6) Turn on the NOX generator O2 (or air) 
supply and adjust the O2 (or air) flow rate so that the NO 
indicated by the analyzer is about 10 percent less than indicated in 
step (5). Record the concentration of NO in this NO + O2 
mixture.
    (7) Switch the NOX generator to the generation mode and 
adjust the generation rate so that the NO measured on the analyzer is 20 
percent of that measured in step (5). There must be at least 10 percent 
unreacted NO at this point. Record the concentration of residual NO.
    (8) Switch the oxides of nitrogen analyzer to the NOX 
mode and measure total NOX. Record this value.
    (9) Switch off the NOX generation but maintain gas flow 
through the system. The oxides of nitrogen analyzer will indicate the 
NOX in the NO + O2 mixture. Record this value.
    (10) Turn off the NOX generator O2 (or air) 
supply. The analyzer will now indicate the NOX in the 
original NO in N2 mixture. This value should be no more than 
5 percent above the value indicated in step (4).
    (11) Calculate the efficiency of the NOX converted by 
substituting the concentrations obtained into the following equation:

Percent Efficiency = [1 + (a-b)/(c-d)] x 100

where:
a = concentration obtained in step (8).
b = concentration obtained in step (9).
c = concentration obtained in step (6).
d = concentration obtained in step (7).


If converter efficiency is not greater than 90 percent corrective action 
will be required.
    (b) Initial and periodic calibration. Prior to its introduction into 
service and monthly thereafter the chemiluminescent oxides of nitrogen 
analyzer shall be calibrated on all normally used instrument ranges. Use 
the same flow rate as when analyzing samples. Proceed as follows:
    (1) Adjust analyzer to optimize performance.
    (2) Zero the oxides of nitrogen analyzer with zero-grade air or 
zero-grade nitrogen.
    (3) Calibrate on each normally used operating range with NO in N2 
calibration gases having nominal concentrations of 15, 30, 45, 60, 75, 
and 90 percent of that range. For each range calibrated, if the 
deviation from a least-squares best-fit straight line is 2 percent or 
less of the value at each data point, concentration values may be 
calculated by use of a single calibration factor for that range. If the 
deviation exceeds 2 percent at any point, the best-fit non-linear 
equation which represents the data to within 2 percent of each test 
point shall be used to determine concentration.
    (c) When testing methanol-fueled vehicles, it may be necessary to 
clean the analyzer frequently to prevent interference with 
NOX measurements (see EPA/600/S3-88/040).

[42 FR 32954, June 28, 1977, as amended at 42 FR 45652, Sept. 12, 1977; 
52 FR 47869, Dec. 16, 1987; 58 FR 58422, Nov. 1, 1993; 60 FR 34347, June 
30, 1995]