[Code of Federal Regulations]
[Title 40, Volume 31]
[Revised as of July 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR1065.308]

[Page 717-719]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 1065_ENGINE-TESTING PROCEDURES--Table of Contents
 
                Subpart D_Calibrations and Verifications
 
Sec.  1065.308  Continuous gas analyzer system-response and updating-recording verification.

    (a) Scope and frequency. Perform this verification after installing 
or replacing a gas analyzer that you use for continuous sampling. Also 
perform this verification if you reconfigure your system in a way that 
would change system response. For example, perform

[[Page 718]]

this verification if you add a significant volume to the transfer lines 
by increasing their length or adding a filter; or if you change the 
frequency at which you sample and record gas-analyzer concentrations.
    (b) Measurement principles. This test verifies that the updating and 
recording frequencies match the overall system response to a rapid 
change in the value of concentrations at the sample probe. Gas analyzer 
systems must be optimized such that their overall response to a rapid 
change in concentration is updated and recorded at an appropriate 
frequency to prevent loss of information.
    (c) System requirements. To demonstrate acceptable updating and 
recording with respect to the system's overall response, use good 
engineering judgment to select one of the following criteria that your 
system must meet:
    (1) The product of the mean rise time and the frequency at which the 
system records an updated concentration must be at least 5, and the 
product of the mean fall time and the frequency at which the system 
records an updated concentration must be at least 5. This criteria makes 
no assumption regarding the frequency content of changes in emission 
concentrations during emission testing; therefore, it is valid for any 
testing.
    (2) The frequency at which the system records an updated 
concentration must be at least 5 Hz. This criteria assumes that the 
frequency content of significant changes in emission concentrations 
during emission testing do not exceed 1 Hz.
    (3) You may use other criteria if we approve the criteria in 
advance.
    (4) For PEMS, you do not have to meet this criteria if your PEMS 
meets the overall PEMS check in Sec.  1065.920.
    (d) Procedure. Use the following procedure to verify the response of 
a continuous gas analyzer system:
    (1) Instrument setup. Follow the analyzer system manufacturer's 
start-up and operating instructions. Adjust the system as needed to 
optimize performance.
    (2) Equipment setup. Using minimal gas transfer line lengths between 
all connections, connect a zero-air source to one inlet of a fast-acting 
3-way valve (2 inlets, 1 outlet). Using a gas divider, equally blend an 
NO-CO-CO2-C3H8-CH4 (balance 
N2) span gas with a span gas of NO2. Connect the 
gas divider outlet to the other inlet of the 3-way valve. Connect the 
valve outlet to an overflow at the gas analyzer system's probe or to an 
overflow fitting between the probe and transfer line to all the 
analyzers being verified.
    (3) Data collection. (i) Switch the valve to flow zero gas.
    (ii) Allow for stabilization, accounting for transport delays and 
the slowest instrument's full response.
    (iii) Start recording data at the frequency used during emission 
testing. Each recorded value must be a unique updated concentration 
measured by the analyzer; you may not use interpolation to increase the 
number of recorded values.
    (iv) Switch the valve to flow the blended span gases.
    (v) Allow for transport delays and the slowest instrument's full 
response.
    (vi) Repeat the steps in paragraphs (d)(3)(i) through (v) of this 
section to record seven full cycles, ending with zero gas flowing to the 
analyzers.
    (vii) Stop recording.
    (e) Performance evaluation. (1) If you chose to demonstrate 
compliance with paragraph (c)(1) of this section, use the data from 
paragraph (d)(3) of this section to calculate the mean rise time, 
T10-90, and mean fall time, T90-10, for each of 
the analyzers. Multiply these times (in seconds) by their respective 
recording frequencies in Hertz (1/second). The value for each result 
must be at least 5. If the value is less than 5, increase the recording 
frequency or adjust the flows or design of the sampling system to 
increase the rise time and fall time as needed. You may also configure 
digital filters to increase rise and fall times.
    (2) If a measurement system fails the criterion in paragraph (e)(1) 
of this section, ensure that signals from the system are updated and 
recorded at a frequency of at least 5 Hz.
    (3) If a measurement system fails the criteria in paragraphs (e)(1) 
and (2) of this section, you may use the continuous analyzer system only 
if the deficiency does not adversely affect your

[[Page 719]]

ability to show compliance with the applicable standards.