**STANDARD OPERATING PROCEDURES**

**THERMO ENVIRONMENTAL INSTRUMENTS**

**42CY NO~y~ TRACE LEVEL**

**REACTIVE NITROGEN COMPOUNDS INSTRUMENT**

# **Version 1.1** 

![](media/image1.png){width="1.6583333333333334in"
height="1.6111111111111112in"}

**Section 1.1 Acknowledgments**

This Standard Operating Procedure (SOP) for Trace Level Reactive
Nitrogen Compounds is the product of EPA's Office of Air Quality,
Planning and Standards. The following individuals are acknowledged for
their contributions.

**Principal Author**

Kevin A. Cavender, OAQPS-EMAD, Research Triangle Park, NC 27711

**Reviewers**

Office of Air Quality, Planning and Standards

Joann Rice, Trace Gas Team Lead, OAQPS-EMAD, Research Triangle Park, NC
27711

Anna Kelly, OAQPS-EMAD, Research Triangle Park, NC 27711

Keith Kronmiller, Mantech, Inc. Research Triangle Park, NC 27711

**Comments and questions can be directed to:**

Kevin A. Cavender

EPA-OAQPS

Emission, Analysis and Monitoring Division

Mail Drop C339-02

Research Triangle Park, NC 27711

Email: [cavender.kevin@epa.gov](mailto:mikel.dennisk@epa.gov)

Phone: (919)-541-2364

**Section 2.0 Table of Contents**

+------------------------------------------------------------+---------+
| Section                                                    | Page    |
+------------------------------------------------------------+---------+
| 1.0 Title Page                                             | 1       |
+------------------------------------------------------------+---------+
| 1.  Acknowledgements                                       | 2       |
+------------------------------------------------------------+---------+
| 2.0 Table of Contents                                      | 3       |
+------------------------------------------------------------+---------+
| 2.1 List of Tables and Figures                             | 4       |
+------------------------------------------------------------+---------+
| 3.0 Procedures                                             | 5       |
+------------------------------------------------------------+---------+
| 3.1 Scope and Applicability                                | 5       |
+------------------------------------------------------------+---------+
| 3.2 Summary of Method                                      | 5       |
+------------------------------------------------------------+---------+
| 3.3 Definitions                                            | 7       |
+------------------------------------------------------------+---------+
| 3.4 Health and Safety Warnings                             | 7       |
+------------------------------------------------------------+---------+
| 3.5 Cautions                                               | 7       |
+------------------------------------------------------------+---------+
| 3.6 Interferences                                          | 8       |
+------------------------------------------------------------+---------+
| 3.7 Personal Qualifications                                | 8       |
+------------------------------------------------------------+---------+
| 3.8 Equipment and Supplies                                 | 8       |
+------------------------------------------------------------+---------+
| 3.9 Procedure                                              | 10      |
+------------------------------------------------------------+---------+
| 3.9.1 Sample Collection                                    | 10      |
+------------------------------------------------------------+---------+
| 3.9.2 Sample Handling and Preservation                     | 10      |
+------------------------------------------------------------+---------+
| 3.9.3 Instrument Operation, Start up and Maintenance       | 10      |
+------------------------------------------------------------+---------+
| 3.9.3.1 Start up                                           | 10      |
+------------------------------------------------------------+---------+
| 3.9.3.2 Operation and Range Setting                        | 11      |
+------------------------------------------------------------+---------+
| 3.9.9.3 Diagnostic Checks/Manual Checks                    | 12      |
+------------------------------------------------------------+---------+
| 3.9.3.4 Preventive Maintenance                             | 13      |
+------------------------------------------------------------+---------+
| 3.9.3.5 Instrument Troubleshooting                         | 13      |
+------------------------------------------------------------+---------+
| 3.9.4 Calibration and Standardization                      | 13      |
+------------------------------------------------------------+---------+
| 3.9.4.1 Adjustment to Zero Air                             | 14      |
+------------------------------------------------------------+---------+
| 3.9.4.2 Adjustment to Calibration Gas                      | 14      |
+------------------------------------------------------------+---------+
| 3.10 Data Analysis and Calculations                        | 15      |
+------------------------------------------------------------+---------+
| 4.0 Quality Control and Quality Assurance                  | 15      |
+------------------------------------------------------------+---------+
| 4.1 Precision                                              | 15      |
+------------------------------------------------------------+---------+
| 4.2 Bias                                                   | 15      |
+------------------------------------------------------------+---------+
| 4.3 Representativeness                                     | 16      |
+------------------------------------------------------------+---------+
| 4.4 Completeness                                           | 16      |
+------------------------------------------------------------+---------+
| 4.5 Comparability                                          | 16      |
+------------------------------------------------------------+---------+
| 4.6 Method Detection Limit                                 | 16      |
+------------------------------------------------------------+---------+
| 5.0 References                                             | 17      |
+------------------------------------------------------------+---------+

**List of Tables**

  ------------------------------------------------------------ ----------
  Table Name and Number                                        Page

  3-1 Definition of Key Terms                                  7

  3-2 Diagnostic Checks                                        13

  3-3 Preventive Maintenance Schedule for the 42CY             13

  4-1 Measurement Quality Assurance Objectives                 17
  ------------------------------------------------------------ ----------

**List of Figures**

  ------------------------------------------------------------ ----------
  Figure Name and Number                                       Page

  3-1 Simplified Flow Diagram of 42CY Monitor                  6

  3-2 Schematic of plumbing and wiring for 42CY External       11
  Converter                                                    
  ------------------------------------------------------------ ----------

#### STANDARD OPERATING PROCEDURES

**THERMO ENVIRONMENTAL INSTRUMENTS**

**42CY NO~y~ TRACE LEVEL**

**REACTIVE NITROGEN COMPOUNDS INSTRUMENT**

**3.0 PROCEDURES**

**3.1 Scope and Applicability**

Reactive nitrogen compounds (NO~y~) have been identified as precursors
for both ozone and fine particulate matter (PM~2.5~). Measurements of
NO~y~ constitute a valuable adjunct to current NO and NO~2~ monitoring
because the individual species comprising NO~y~ include not only NO and
NO~2~ but also other organic nitroxyl compounds that have recently been
shown to play a significant role in the photochemical O~3~ formation
process.

NO~y~ consists of all oxides of nitrogen in which the oxidation state of
the N atom is +2 or greater, ie, the sum of all reactive nitrogen oxides
including NO~x~ (NO + NO~2~) and other nitrogen oxides referred to as
NO~z~. The major components of NO~z~ include nitrous acids \[nitric acid
(HNO~3~), and nitrous acid (HONO)\], organic nitrates \[peroxyl acetyl
nitrate (PAN), methyl peroxyl acetyl nitrate (MPAN), and peroxyl
propionyl nitrate, (PPN)\], and particulate nitrates.

NO + NO~2~ + NO~z~ = NO~y~

The Thermo Environmental Instruments (TECO) model 42CY is an instrument
for the determination of trace levels of NO~y~ by its chemiluminescent
reaction with O~3~. This SOP will detail the operation, calibration,
preventive maintenance, cautions and health warnings.

**3.2 Summary of Method**

The analytical principle is based on the chemiluminescent reaction of NO
with an excess of O~3~. This reaction produces a characteristic near
infrared luminescence with an intensity that is linearly proportional to
the concentration of NO present. Specifically,

NO + O~3~ → NO~2~ + O~2~ + h~ν~

where:

h~ν~ = emitted photon energy

The reaction results in electronically excited NO~2~ molecules which
revert to their ground state, resulting in an emission of light or
chemiluminescence.

To determine the concentration of NO, the sample gas is blended with
O~3~ in a reaction chamber causing the reaction to occur. The
chemiluminescence that results from the reaction is monitored by an
optically filtered high-sensitivity photomultiplier. The optical filter
and photomultiplier respond to light in a narrow-wavelength band unique
to the NO and O~3~ reaction. The electronic signal produced in the
photomultiplier is proportional to the NO concentration.

To measure NO~y~, sample air is passed through a probe-mounted chemical
reduction converter and the nitroxyl compounds present are reduced to
NO. The sample is then blended with O~3~ and the chemiluminescent
response is proportional to the concentration of NO~y~ entering the
converter. The chemical reduction converter uses heated molybdenum to
convert non-NO NO~y~ species to NO. Specifically,

NO~2/Z~ + Mo → NO + MoO~3~

where:

Mo = heated molybdenum reductant

The concentration of NO~2~ + NO~z~ is calculated as the difference
between a measured NO~y~ value and a measured NO value representing
approximately the same point in time. This procedure is similar to the
current methodology used to measure NO~x~, however, the converter
temperature is higher in order to enhance conversion of NO~z~ species.
In addition, the converter has been moved to the sample inlet to avoid
line losses of "sticky" NO~y~ species such as HNO~3~.

A diagram of the 42CY instrument is presented in Figure 3-1. For the
42CY, ambient sample is first drawn through a short Teflon sample line
and split into two parallel flow channels using a ½ inch PFT Teflon tee.
Channel 1 passes through a Teflon filter and then directly to the
monitor. Channel 2 first passes through a catalytic converter before
going through a Teflon filter to the monitor. Flow from each channel is
alternately fed to the reaction chamber to detect the NO. The converter
is operated outside of the analyzer, close to the ambient sampling
point. This allows for a short flow path upstream of the converter and
minimizes the loss of species such as HNO~3~. In addition to alternating
flows from Channel 1 and Channel 2 to the reactor, the analyzer also
alternates a flow of internal zero air, produced by pre-reacting the
sample flow with a high concentration of ozone before reaching the
chemiluminescent detector. The signal from this zero air stream is used
to correct for analyzer drift, and allows the analyzer to achieve very
low detection limits (0.05 ppb) compared with standard NO~x~ analyzers.

![](media/image2.png){width="5.308333333333334in"
height="4.251388888888889in"}

**Figure 3-1. Simplified Flow Diagram of 42CY NO~y~ Monitor**

**3.3 Definitions**

Here are some key terms for this method.

**Table 3-1, Definitions of Key Terms**

  ----------------------- -----------------------------------------------
  [Term]{.underline}      Definition

  NO~y~                   Total reactive nitrogen including NO, NO~2~,
                          HNO~3~, and other reactive organic nitrogen
                          compounds.

  NO~z~                   Reactive nitrogen compounds other than NO and
                          NO~2~.

  DAS                     Data acquisition system. Used for automatic
                          collection and recording of Carbon Monoxide
                          concentrations.

  Interferences           Physical or chemical entities that cause NO~y~
                          measurements to be higher (positive) or lower
                          (negative) than they would be without the
                          entity. (See Section 3.6).
  ----------------------- -----------------------------------------------

**3.4 Health and Safety Warnings**

[To prevent personal injury, please heed these warnings concerning the
42CY.]{.underline}

1.  Nitrogen oxides are a poisonous gas. Vent any nitrogen oxide or
    calibration span gas to the atmosphere rather than into the shelter
    or other sampling area. If this is impossible, limit exposure to
    nitrogen oxide by getting fresh air every 5 to 10 minutes. If the
    operator experiences light headedness, headache or dizziness, leave
    the area immediately.

2.  Always use a third ground wire on all instruments.

3.  Always unplug the analyzer when servicing or replacing parts.

4.  If it is mandatory to work inside an analyzer while it is in
    operation, use extreme caution to avoid contact with high voltages.
    The analyzer has a 110 volt Volts Alternating Current (VAC) power
    supply. Refer to the manufacturer\'s instruction manual and know the
    precise locations of the VAC components before working on the
    instrument.

5.  Avoid electrical contact with jewelry. Remove rings, watches,
    bracelets, and necklaces to prevent electrical bums.

**3.5 Cautions**

[To prevent damage to the 42CY, all cautions should immediately precede
the applicable step in this SOP. The following precautions should be
taken:]{.underline}

1.  Keep the interior of the analyzer clean.

2.  Inspect the system regularly for structural integrity.

3.  To prevent major problems with leaks, make sure that all sampling
    lines are reconnected after required checks and before leaving the
    site.

4.  Inspect tubing for cracks and leaks.

5.  It is recommended that the analyzer be leak checked after
    replacement of any pneumatic parts.

6.  If cylinders are used in tandem with Mass Flow Control (MFC)
    calibrators, use and transport is a major concern. Gas cylinders can
    sometimes contain pressures as high as 2000 pounds per square inch
    (psi). Handling of cylinders must be done in a safe manner. If a
    cylinder is accidentally dropped and valve breaks off, the cylinder
    can become explosive or a projectile.

7.  Transportation of cylinders is regulated by the Department of
    Transportation (DOT). It is strongly recommended that all agencies
    contact the DOT or Highway Patrol to learn the most recent
    regulations concerning transport of cylinders.

8.  Low levels of nitrogen oxides in the air can irritate your eyes,
    nose, throat, and lungs, possibly causing you to cough and
    experience shortness of breath, tiredness, and nausea. Exposure to
    low levels can also result in fluid build-up in the lungs 1 or 2
    days after exposure. Breathing high levels of nitrogen oxides can
    cause rapid burning, spasms, and swelling of tissues in the throat
    and upper respiratory tract, reduced oxygenation of body tissues, a
    build-up of fluid in your lungs, and death.

9.  It is possible (and practical) to blend other compounds with NO. If
    this is the case, it is recommended that MSDS for all compounds be
    made available to all staff that use and handle the cylinders or
    permeation tubes.

10. Shipping of cylinders is governed by the DOT. Contact the DOT or
    your local courier about the proper procedures and materials needed
    to ship high-pressure cylinders.

**3.6 Interferences**

**Ammonia:** Depending on the converter temperature, the converter may
convert a small amount of ammonia (NH~3~) to NO, resulting in increased
NO readings. However, under normal circumstances NH~3~ concentrations
are low compared to NO and this positive interference is negligible.
Nonetheless, care should be taken when siting the monitor to be sure
that it is not located near significant NH~3~ sources which could cause
elevated NH~3~ concentrations (e.g., concentrated animal feeding
operations).

**3.7 Personal Qualifications**

The person(s) chosen to operate the 42CY should have a minimum of
qualifications. The understanding of basic chemistry and electronics are
a must. The understanding of digital circuitry is helpful, but not
required. Also, courses in data processing and validation are also
welcome.

**3.8 Equipment and Supplies**

**Monitoring Apparatus:** The design of the 42CY is similar to the 42C
with several major variations. A diagram of the 42CY instrument is
presented in Figure 3-1. The four main components are:

-   *[Remote Inlet and Converter:]{.underline}* This component consists
    of a weather resistant enclosure that houses the molybdenum
    converter and supports the sample inlet.

-   *[Pneumatic System:]{.underline}* Consists of sample inlet lines,
    sample bypass pump, particulate filters, reaction chamber,
    flowmeters, and vacuum pump, all used to bring ambient air samples
    to the analyzer.

-   *[Analytical System]{.underline}*: This portion of the instrument
    consists of the ozone generator, pre-reaction chamber, reaction
    chamber, and photomultiplier tube.

-   *[Electronic Hardware:]{.underline}* The part of the analyzer that
    generally requires little or no maintenance. If the 42CY is operated
    above the manufacturer\'s recommended temperature limit, however,
    individual integrated chips can fail and cause problems with data
    storage or retrieval.

Other apparatus and equipment includes the following.

**Instrument Shelter:** A shelter is required to protect the analyzer
from precipitation and adverse weather conditions, maintain operating
temperature within the analyzer\'s temperature range requirements, and
provide security and electrical power. The recommended shelter
temperature range is 20-30^o^C.

**Spare Parts and Incidental Supplies:**. See the 42CY operating manual,
Chapter 5, for specific maintenance and replacement requirements.

**Calibration System**: A system that creates concentrations of nitrogen
oxide of known quality is necessary for establishing traceability. The
calibration system must also include a high precision ozone generator in
order to generate concentrations of nitrogen dioxide by gas phase
titration with nitrogen oxide. This is described in detail in the
"Calibration of Trace Gas Instruments SOP." Please reference this
document.

**DAS**: A data acquisition system is necessary for storage of ambient
and ancillary data collected by the 42CY. The 42CY requires a minimum of
two analog outputs, one each for NO and NO~y~ outputs. A third output is
also needed if the monitor is to be run in auto-ranging mode to capture
the range information. Note, a digital DAS is preferred because
diagnostic information can also be collected which will greatly help
troubleshooting and validation of data. This is detailed in the "Data
Acquisition and Management SOP."

**Wiring, Tubing and Fittings***:* PFT Teflon™ should be used
exclusively throughout the intake system. Examine the tubing and discard
if particulate matter is collects in the tubing. All fittings and
ferrules should be made of Teflon™ or stainless steel. Connection wiring
to the DAS should be shielded two strand wire or RS-232 cables for
digital connections.

**Reagents and Standard:** The 42CY does not require any reagents since
the instrument uses photometry to analyze for NO~y~. All standards for
the NO~y~ method can be obtained in compressed cylinders and must be
NIST traceable. Please see the "Calibration of Trace Gas Analyzers" SOP.

**3.9 Procedure**

**3.9.1 Sample Collection:** Ambient air is drawn through a sample inlet
located on the remote inlet/converter. The sampling point should be
located 3 to 5 meters above ground level, at least 1 meter from all
obstructions, and at least 10 meters from obstructions over a range of
at least 180 degrees. These requirements necessitate mounting the
catalytic converter outside the shelter. The sample bypass lines from
the converter to the instrument should not exceed 10 meters in length.

**3.9.2 Sample Handling and Preservation:** NO~y~ samples receive no
special preparation prior to analysis. Therefore this SOP does not need
a section on Sample Handling and Preservation.

**3.9.3 Instrument Operation, Startup and Maintenance**

This section discusses startup, operation and maintenance of the
42C-NOY. The 42CY series instrument has a digital front panel screen
with control buttons below. This allows the user to check functions,
switch operating parameters, adjust zero and span and read warnings
messages. **It is extremely important that the user familiarize
themselves with the menus available. Inadvertently changing parameters
within the analyzer can damage the instrument and possibly invalidate
data as well. Please reference the 42CY owner's manual and read it
carefully before adjusting any parameters that are set by the factory.**

**3.9.3.1 Installation and Start up**

1.  Before the instrument is operated, inspect the instrument for any
    damage. If damage is observed to the shipping box or the instrument,
    contact your shipping personnel.

2.  Remove the instrument from its shipping container and set on a table
    or bench that allows easy access to both the front and read or the
    instrument.

3.  Carefully remove the instrument cover and remove any packing
    material.

4.  Check for possible internal damage.

5.  Check that all connectors and printed circuit boards are firmly
    attached.

6.  Once you have performed your inspection, replace the cover.

7.  Remove the remote inlet enclosure and place on a bench that allows
    easy access.

8.  Open the enclosure and check for internal damage.

9.  Using ¼ inch PFT Teflon^TM^ tubing, plumb the inlet as shown in
    Figure 3-2.

10. Mount the enclosure at the desired sampling location being sure to
    meet the requirements detailed in 3.9.1, above.

11. Determine the distance from the point where the sample tubing exits
    the converter enclosure to the point where the tubing will enter the
    monitoring station, including ample length to account for any curves
    or obstructions. Cut the two plastic conduits to this length.

12. Run the two sample lines, calibration line, and thermocouple wire
    through one conduit, and the converter power cable through the
    second.

13. Connect the two sample lines, calibration line, thermocouple wire,
    and power cable inside the converter enclosure as shown in Figure
    3-2, and secure the conduits to the converter enclosure.

14. Run the tubing, thermocouple wire, and power cable in to the
    monitoring station.

15. Mount the 42CY in its rack being sure that the 42CY has enough
    clearance so that it gets proper ventilation.

16. Connect the sample lines to the bypass pump, filters, and analyzer
    as shown in Figure 3-1.

17. Connect the Dryrite^TM^ air dryer to the dry air bulkhead.

18. Connect the intake of the vacuum pump to the exhaust bulkhead.

19. Connect the charcoal container to the outlet of the vacuum pump.

20. Connect the converter power cable and thermocouple wire to the back
    of the 42CY.

21. Connect the power cable and plug the instrument, vacuum pump, and
    bypass pump into a grounded power strip that has surge protection.
    It is also advisable to purchase an Uninterrupted Power Supply
    (UPS). An UPS will protect the 42CY from power surges and keep the
    unit operating until an operator can shut it down.

22. Connect the output of the analog to a DAS via shielded two wire
    cable. Please see EPA SOP on "Data Management" for details.

23. Connect the digital RS-232 port to an appropriate cable and connect
    it to the DAS. Please see EPA SOP on "Data Management" for further
    details.

24. Press the power rocker switch to "ON."

25. After an adequate warm-up period, run through the menu and record
    factory/start-up settings. Compare to recommended limits located in
    the manual and listed on the daily worksheet.

![](media/image3.png){width="6.489583333333333in"
height="3.6041666666666665in"}

F**igure 3-2. Schematic of plumbing and wiring for 42CY External
Converter**

**3.9.3.2 Operation and Range Setting**

1.  The exhaust fan will start and the Power-Up and Self-Test screens
    will be displayed. These screens are displayed each time the
    instrument is turned on, and will continue to be displayed till the
    instrument has completed its warm up and self-checks. You should
    allow 30 minutes for the instrument to stabilize.

2.  After the warm-up period the Run screen, the normal operating
    screen, is displayed. This screen is where the NO and NO~y~
    concentration is displayed. The display for the model that EPA is
    using currently mis-reports the data. The data reported as NO~x~ is
    actually NO~y~. The data reported as NO~2~ is actually NO2 + NO~z~.
    Future versions should correct this, and are expected to report NO,
    NO~y~ and "DIFF" which would represent NO2 + NO~z~.

3.  In the bottom right hand corner the word "**LOCAL**" or "**REMOTE**"
    will be displayed. The analyzer must be in local mode to adjust the
    configuration using the keys on the front panel. Press the **ENTER**
    button until the analyzer is in local mode.

4.  From the Run screen, the Main Menu, which contains a list of
    submenus, can be displayed by pressing the **MENU** pushbutton.

5.  Instrument parameters and features are divided into the submenus
    according to their function. Use the **UP/DOWN ARROW** pushbuttons
    to move the cursor to each submenu. **Note:** When the Main Menu is
    entered directly from the Run screen, the **LEFT ARROW** pushbutton
    may be used to jump to the most recently displayed submenu screen.

6.  To set the range for the instrument, press the **DOWN ARROW**
    pushbutton till the cursor is on "Range." Press the **ENTER**
    pushbutton to display the Range Menu.

7.  In the upper right corner of the display, the word single, dual, or
    auto is displayed to indicate the active mode. For a detailed
    explanation about the single, dual, or autorange mode, see Chapter 3
    (page 3-7) of the manual. This SOP addresses setting the range for a
    single range.

8.  Press the **ENTER** pushbutton for the Gas Units screen. Use the
    **DOWN ARROW** pushbutton to select "PPB" and press **ENTER**. Press
    **MENU** to return to the Range Menu.

9.  Use the **DOWN ARROW** pushbutton to display the Range screen and
    press **ENTER**.

10. Use the **UP/DOWN ARROW** pushbuttons to scroll through the preset
    ranges. Select "100.0" and press **ENTER**. Press **MENU** to return
    to the Range Menu. Note, a higher range may be required in areas
    with higher NO~y~ concentrations.

11. Press **RUN** to return to the Run screen.

12. To set the averaging time, press the **MENU** button to return to
    the Main Menu. Press the **DOWN ARROW** pushbutton till the cursor
    is on Averaging Time.

13. Press **ENTER** for the averaging time screen. Use the **DOWN
    ARROW** pushbutton to select the desired averaging time and press
    **ENTER**. Press **RUN** to return to the Range Menu.

14. To set the correct time and date on the instrument, press **MENU**
    to return to the Main Menu. Press the **DOWN ARROW** pushbutton till
    the cursor is on Instrument Controls. Press **ENTER** to display the
    Instrument Controls screen.

15. Use the **UP/DOWN ARROW** pushbuttons to scroll through the choices.
    Select "Time" and press **ENTER**.

16. Use the **UP/DOWN ARROW** pushbuttons to increase/decrease the hours
    and minutes; use the **LEFT/RIGHT ARROW** pushbuttons to move the
    cursor left and right. Set the appropriate time and press **ENTER**.
    Press **MENU** to return to the Instrument Controls screen.

17. Select "Date" and press **ENTER**.

18. Use the **UP/DOWN ARROW** pushbuttons to increase/decrease the
    month, day, and year; use the **LEFT/RIGHT ARROW** pushbuttons to
    move the cursor left and right. Set the appropriate date and press
    **ENTER**. Press **RUN** to return to the Run screen.

19. The instrument is now set with the appropriate time, date and full
    scale range.

20. It is recommended that you allow the 42CY 24 hours before you
    attempt function checks or calibration.

21. If the DAS system that you have does not have the RS-232
    capabilities, then proceed to the next section, Diagnostic
    Checks/Manual Checks. If you have connected the 42CY to a computer
    or DAS, review the Diagnostic Check from your computer screen.

**3.9.3.3 Diagnostic Checks/Manual Checks**

To determine whether the 42CY is working properly, the field operators
should perform the Diagnostic Checks every time they visit the
monitoring station. It is good practice for the operator to check these
Diagnostic Checks either by the computer or manually. Below are
instructions on how to perform this manually. Please note that the 42CY
has set upper and lower ranges for some of these Diagnostic checks.
Please reference the owner's manual for these ranges.

1.  To display the Diagnostics menu, from the Run screen press the
    **MENU** pushbutton to display the Main Menu. Use the **UP/DOWN
    ARROW** pushbuttons to move the cursor to "Diagnostics." Press
    **ENTER** for the Diagnostics screen.

2.  Use the **UP/DOWN ARROW** pushbuttons to toggle through the function
    check tree. The following table illustrates the functions that
    should be recorded. Please see Chapter 3 (page 3-36) 42CY manual for
    more details. A manual checklist on maintenance is attached in
    Appendix A of this SOP.

3.  On the Program Number screen, the version numbers of the program
    installed are displayed. Prior to contacting the factory with any
    questions regarding the instrument, note the program numbers.

## Table 3-2 Diagnostic Checks

  --------------- -------------------------------------------------------
  Check           Explanation

  Voltages        The current DC power supply and PMT power supply
                  voltages

  Temperatures    The current internal instrument and chamber
                  temperatures

  Pressure        The current chamber pressure

  Flow            The current ozonator and sample flow rate

  Test Analog     Enable analog outputs to be set to zero and full scale
  Outputs         to adjust analog outputs to agree with the front panel
                  display
  --------------- -------------------------------------------------------

## Reference the owners manual or the worksheet in Appendix A of this SOP for acceptable limits. Once the Diagnostic checks have been established and recorded for the 42CY, it is time to calibrate the instrument. Please refer to section 3.9.4 of this SOP.

**3.9.3.4 Preventive Maintenance**

Preventive maintenance should prevent down-time and data loss. Table 3.3
lists the preventive maintenance items that are listed in the 42CY
manual, section 5.

**Table 3-3 Preventive Maintenance Schedule the TECO 42CY**

**Item** **Schedule**

Replace ozonator air feed drying column As needed

Inspect and replace sample filters Weekly

Inspect and replace capillaries Quarterly

Digital to analog converter test As needed

Inspect and clean cooler fins Semi-annually

Inspect and clean fan filters Semi-annually

**3.9.3.5 Instrument Troubleshooting**

The 42CY manual has an excellent troubleshooting guide in Chapter 6.
Please reference the manual for details on troubleshooting the 42CY
analyzer.

**3.9.4 Calibration and Standardization**

The calibration of the 42CY is performed by comparing the output of the
instrument against standardized gases of known quality. Generation of
these gases is detailed in the "Calibration of Trace Gas Analyzers" SOP.
This section will detail how to adjust the 42CY to the standardized
gases. Once the calibration has been performed, compare the response of
your DAS to the calculated "source" value. If this is outside of +/-10%,
then adjust the instrument response as detailed in the next sections.

**3.9.4.1 Adjustment to Zero Air**

In order to adjust the output of the 42CY to zero air, perform the
following:

1.  Connect the calibration line to a source of zero air. Supply a
    sufficient amount of zero air to supply the analyzer and to ensure
    that a small amount of excess zero air exits from the sample inlet.

2.  Allow the analyzer to sample zero air for at least 15 minutes or
    until stable NO, NO~y~, and NO~2~+NO~z~ readings are obtained.

3.  From the Main Menu, choose Calibration. From the calibration menu,
    choose Calibrate Zero.

4.  The Calibrate Zero screen displays the NO, NO~y~, and Prereactor
    readings.

5.  Press **ENTER** to set the NO, NO~y~, and Prereactor readings to
    zero.

6.  The message "Savings Parameters(s)" is briefly displayed to indicate
    that the background readings have been set to zero.

7.  Press **MENU** to return to the Calibration menu.

8.  Press **RUN** to return to the Run screen.

**3.9.4.2 Adjustment to Calibration Gas**

In order to adjust the output of the 42CY to NIST traceable calibration
gas, perform the following:

1.  Switch the calibration unit to generate a known concentration of NO
    corresponding to approximately 80% of full scale.

2.  Supply a sufficient amount of calibration air to supply the analyzer
    and to ensure that a small amount of excess calibration air exits
    from the sample inlet.

3.  Allow the instrument to sample calibration gas for a minimum of 15
    minutes, or until stable NO, NO~y~, and NO~2~+NO~z~ readings are
    obtained.

4.  From the Main Menu select the Calibration menu; select the
    "Calibrate NO" screen.

5.  On the bottom line, there will be individual digits with which the
    span value can be set. In order to change the span value, use the
    **UP/DOWN ARROW** pushbuttons to increase/decrease each digit; use
    the **LEFT/RIGHT ARROW** pushbuttons to move the cursor left and
    right.

6.  Change the span value to reflect the known concentration of NO in
    the calibration gas being sampled.

7.  Press **ENTER** to calibrate the NO reading to the NO calibration
    gas.

8.  This operation changes the calculation equation and adjusts the NO
    span coefficient of the instrument.

9.  Press **MENU** to return to the Calibration menu.

10. Select "Calibrate NO~y~".

11. Change the span value to reflect the known concentration of NO plus
    any known NO~2~ impurity in the calibration gas being sampled.

12. Press **ENTER** to calibrate the NO~y~ reading to the NO calibration
    gas.

13. This operation changes the calculation equation and adjusts the
    NO~y~ span coefficient of the instrument.

14. Press **MENU** to return to the Calibration menu.

15. Adjust the calibrator to add a known concentration of ozone to the
    calibration gas corresponding to approximately 60% of full scale.
    The ozone will react with the NO in the calibration gas to form
    NO~2~.

16. Supply a sufficient amount of calibration air to supply the analyzer
    and to ensure that a small amount of excess calibration air exits
    from the sample inlet.

17. Allow the instrument to sample calibration gas for a minimum of 15
    minutes, or until stable NO, NO~y~, and NO~2~+NO~z~ readings are
    obtained.

18. Select "Calibrate NO2" from the Calibration menu.

19. Change the span value to reflect the known concentration of ozone
    added to the calibration gas plus any known NO~2~ impurity in the
    calibration gas being sampled.

20. Press **ENTER** to calibrate the NO~2~ reading to the NO calibration
    gas.

21. This operation changes the calculation equation and adjusts the
    NO~2~ span coefficient of the instrument.

22. Press **RUN** to return to the Run screen.

    **3.10 Data Analysis and Calculations**

    Data analysis for this analyzer is detailed in "Data Acquisition and
    Management" SOP.

**4.0 QUALITY CONTROL AND QUALITY ASSURANCE**

The following section has brief definitions of the QA/QC indicators.
Table 4-1 has the Measurement Quality Objectives (MQOs) of the 42CY.
Please note that this section details primarily with the data quality
indicators. Quality Control for continuous electronic instruments, such
as the 42CY consists of performing the diagnostic checks, maintenance
and calibrations. These procedures are detailed in sections 3.9.3 and
3.9.4: Instrument Operation, Startup and Maintenance and Calibration and
Standardization. Appendix A has an example of a Quality Control and
Maintenance Record developed by the EPA for this instrument.

**4.1 Precision**

Precision is defined as the measure of agreement among individual
measurements of the same property taken under the same conditions. For
NO~y~, this refers to testing the NO~y~ analyzer in the field at
concentrations between 0.2 and 100 ppb (note, higher test levels may be
required in areas with higher NO~y~ concentrations). The test must be
performed, at a minimum, once every two weeks. Calculations for
Precision can be found in Reference 4.

**4.2 Bias**

Bias is defined as the degree of agreement between a measured value and
the true, expected, or accepted value. Quantitative comparisons are made
between the measured value and the true, standard value during audits.
Generally, three upscale points and a zero point are compared. Two audit
types commonly used for NO~y~, direct comparison and blind, are
discussed below. The SOP should discuss plans for each type of audit.

-   **Direct Comparison Audits:** An independent audit system is brought
    to the monitoring location and produces gas concentrations that are
    assayed by the monitoring station\'s NO~y~ analyzer. In most cases,
    a person outside of the agency or part of an independent QA group
    within the agency performs the audit. The responses of the on-site
    analyzer are then compared against the calculated concentration from
    the independent audit system and a linear regression is generated

-   **Blind Audits:** In blind audits (also called performance
    evaluation audits); agency staff are sent an audit device, such as
    the National Performance Evaluation Program (NPEP). The agency staff
    does not know the NO~y~ concentrations produced by the audit
    equipment. Responses of the on-site analyzer are then compared
    against those of the generator and a linear regression is
    calculated.

**4.3 Representativeness**

Representativeness refers to whether the data collected accurately
reflect the conditions being measured. It is the data quality indicator
most difficult to quantify. Unless the samples are truly representative,
the other indicators are meaningless. Since the NCORE Level I and II
siting criteria are urban and regional, the TL-NO~y~ criteria are the
same. Please reference the National Monitoring Strategy^5^ for a
discussion of NCORE Level II NO~y~ monitoring scale.

**4.4 Completeness**

Completeness is defined as the amount of data collected compared to a
pre-specified target amount. The EPA does not have a minimum
completeness requirement for NO~y~ sampling. However, for NO~x~, EPA
requires a minimum completeness of 75% (40 CFR 50, App.H.3). Typical
completeness with the 42CY values can approach 90-93%.

**4.5 Comparability**

Comparability is defined as the process of collecting data under
conditions that are consistent with those used for other data sets of
the same pollutant. The 42CY meets the MQOs for a Trace Level NO~y~
instrument. Please see Table 4-1.

**4.6 Method Detection Limit**

The method detection limit (MDL) or detectability refers to the lowest
concentration of a substance that can be determined by a given
procedure. The 42CY must be able to detect a minimum value of 50 ppt of
NO~y~.

Table 4-1 Measurement Quality Assurance Objectives

+---------+-----------+--------------------+----------+---------------+
| *       | **Fr      | **Acceptance       | **Ref    | **Information |
| *Requir | equency** | Criteria**         | erence** | or Action**   |
| ement** |           |                    |          |               |
+---------+-----------+--------------------+----------+---------------+
| Bias    | NCORE,    | Slope: 1.00 +/-    | 40 CFR   | Use of NIST   |
|         | once per  | 0.15               | Pt.58    | generated gas |
|         | year      |                    |          | c             |
|         |           | Intercept: +/- 3%  |          | oncentrations |
|         |           | of full scale      |          | with Mass     |
|         |           |                    |          | Flow          |
|         |           | Regression:        |          | Calibration   |
|         |           | \<0.9950           |          | unit that is  |
|         |           |                    |          | NIST          |
|         |           |                    |          | traceable     |
+---------+-----------+--------------------+----------+---------------+
| Pr      | 1 every 2 | Concentration: 0.2 | 40 CFR   | If CV is      |
| ecision | weeks     | -600 ppb,          | Pt.58    | greater than  |
|         |           | Coefficient of     | Appendix | 15%,          |
|         |           | Variance less than | A        | institute     |
|         |           | 15%.               |          | Quality       |
|         |           |                    |          | Control       |
|         |           |                    |          | measures      |
+---------+-----------+--------------------+----------+---------------+
| Compl   | Q         | NCORE, 75%         | National | If under 75%, |
| eteness | uarterly, |                    | Mo       | institute     |
|         | Annually  |                    | nitoring | Quality       |
|         |           |                    | S        | Control       |
|         |           |                    | trategy. | Measures      |
+---------+-----------+--------------------+----------+---------------+
| Repr    | N/A       | Neighborhood,      | 40 CFR   | N/A           |
| esentat |           | Urban or Regional  | 58       |               |
| iveness |           | Scale              |          |               |
+---------+-----------+--------------------+----------+---------------+
| Compar  | N/A       | Must be a Trace    | National | N/A           |
| ability |           | Level instrument.  | Mo       |               |
|         |           | See Sections 3.1   | nitoring |               |
|         |           | and 3.2 of this    | S        |               |
|         |           | document.          | trategy. |               |
+---------+-----------+--------------------+----------+---------------+
| Method  | NA        | 50 ppt             | National | Testing is    |
| De      |           |                    | Mo       | performed at  |
| tection |           |                    | nitoring | the factory.  |
| Limit   |           |                    | Strategy |               |
+---------+-----------+--------------------+----------+---------------+

**5.0 REFERENCES**

1.  Merck Index, twelfth edition 1996, page 296

2.  Seinfeld, John H., Atmospheric Chemistry and Physics of Air
    Pollution, 1986, page 54

3.  Code of Federal Regulations, Title 40, Part 53.23c

> 4\. Code of Federal Regulation, Title 40, Part 58, Appendix A
>
> 5\. The National Air Monitoring Strategy, Final Draft, 4/29/04,
> <http://www.epa.gov/ttn/amtic/monstratdoc.html>

6\. Model 42CY Instruction Manual, Thermo Environmental Instruments

**Appendix A**Number range CHAPTER

Number range CHAPTEREnvironmental Protection Agency

Monthly Quality Control and Maintenance Records

Thermo 42C Trace Level NO/NOy Analyzer

Number range CHAPTERSite Name/Location:
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Technician: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Date/Time: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Instrument: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Serial Number: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Range: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

<table style="width:100%;">
<colgroup>
<col style="width: 13%" />
<col style="width: 8%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 10%" />
<col style="width: 8%" />
<col style="width: 11%" />
<col style="width: 6%" />
<col style="width: 7%" />
<col style="width: 20%" />
</colgroup>
<tbody>
<tr class="odd">
<td><p>Date</p>
<p>Time</p></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>Parameters Acceptance Range</td>
</tr>
<tr class="even">
<td>PMT voltage</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td>+5 volt supply</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>5 +/- 0.5</td>
</tr>
<tr class="even">
<td>+15 volt supply</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>15 +/- 1.5</td>
</tr>
<tr class="odd">
<td>Internal temp</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>15-45 C</td>
</tr>
<tr class="even">
<td>Chamber temp</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>47-51 C</td>
</tr>
<tr class="odd">
<td>Cooler temp</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>-20 - -1 C</td>
</tr>
<tr class="even">
<td>Converter temp</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>300 - 350 C</td>
</tr>
<tr class="odd">
<td>Chamber pressure</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>200 - 400 mm Hg</td>
</tr>
<tr class="even">
<td>Ozonator flow</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>0.05 - 0.15 lpm</td>
</tr>
<tr class="odd">
<td>Sample flow</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>0.1-2 lpm</td>
</tr>
<tr class="even">
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
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<td></td>
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<td></td>
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<td></td>
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</tr>
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<td></td>
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<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr class="even">
<td>Other Tests</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td></td>
<td></td>
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</tr>
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<td></td>
<td></td>
<td></td>
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<td></td>
<td></td>
<td></td>
</tr>
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<td></td>
<td></td>
<td></td>
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<td></td>
</tr>
</tbody>
</table>