Skip to main content
U.S. flag

An official website of the United States government

Air Resource Management Program - Ozone Monitoring Protocols

Jump to a section

Seasonal Instrument Exchange (Calibration Source Only)

Last updated February 1, 2021

Context: Seasonal exchange of calibration source

Tools and equipment needed: laptop with PC200W installed and USB/serial adapter (or Android smartphone with LoggerLink and Bluetooth connector), two spare 2A fuses, inlet filter membrane.

This procedure outlines steps needed to remove a calibration source (the lower of the two instruments) and install a replacement. The calibration sources are exchanged about every six months to ensure data quality.

  1. Download data with your laptop per usual site-visit procedure.

  2. Using the PC200W or LoggerLink display and determine if the installation is in cold weather mode (CW_mode). In LoggerLink, you may have to scroll down to see the CW_mode variable. If the installation is in cold weather mode (CW_mode=true, typically if it is below freezing), use the full procedure. If it is not in cold weather mode (CW_mode=false), skip steps 2 and 6.

  3. If you are using a smartphone, change the display from “Public” to “Status” in the main data display. Scroll down to where you can see the status of datalogger control port 4. Toggle this port to “true” by touching the status for a second or two and using the slider. Then toggle again back to “false”. For laptop users, use the ports dialog in PC200W to toggle this port. This will shut off power to the source’s power connector.

  4. Remove insulation if installed. Remove connections for power, air outlet, and serial cable from rear of calibration source, and detach Velcro strap. While supporting the monitor, remove source from enclosure.

    Ozone measuring instrument with red arrows pointing to the rear of the instrument.
    (USDA Forest Service photo)

  5. Install the new calibration source under the monitor in the enclosure using the Velcro strap. The monitor must be placed on top of the source. Reinstall the thermocouple (brown wire) between the instruments before tightening the strap.

  6. Reattach the air outlet, serial connector and power supply cord to the rear of the source. Reinstall insulation if applicable. Turn on the source rocker switch on the front of the instrument. The instrument will not power-up yet.

  7. Disconnect communication between your smartphone/laptop and the datalogger. Reboot the datalogger by disconnecting its green plug for about five seconds, then plugging it back in. The analyzer should keep running; the source should power-up and go into “hibernation” mode on its own within two minutes. If the source does not power-up, check the fuses; it is common to blow the source’s fuse when exchanging. Re-connect your phone/laptop. In LoggerLink, change back to “Public” data display.

  8. Exchange the inlet filter membrane per usual site-visit procedure. Ensure vacuum is present at the inlet by briefly placing your finger over the inlet on the filter housing. If vacuum is not present, re-check inlet line connections.

  9. Check all data outputs in PC200W or LoggerLink. When you are satisfied that everything is working correctly, disconnect communications, secure the enclosure and depart. Email all data to john.korfmacher@usda.gov at the earliest convenience.

Field Calibration Check Protocol

Last updated April 19, 2024

Context: 2B Technologies Ozone Analyzers

  1. Open equipment enclosure. Record arrival time and average ozone level as displayed on the analyzer. Note any unusual circumstances (e.g., pump not running, display blank, highly variable readings, very hot or cold temperature).

  2. Attach calibration source power leads to battery, plug in calibration source, and check polarity. Turn on source power switch. Attach transfer line to source output and analyzer inlet filter.

  3. Attach Bluetooth serial device to datalogger RS-232 port and plug the device’s power wire into the top pin receptacle on the datalogger CS I/O port. The green LED on the serial device should light up. If not, attach the Bluetooth wire to the 5V port on the datalogger. Establish comms with the datalogger with LoggerLink. If you are using a laptop computer instead of an Android phone, connect your laptop with USB-serial cable and communicate with the datalogger using LoggerNet or PC400W.

  4. If comms with the datalogger fail, ensure the MAC address of the Bluetooth device matches that in the datalogger’s entry in LoggerLink. Also, you may try rebooting the datalogger, removing and reattaching the Bluetooth device, deleting and reinstalling the datalogger in LoggerLink, and resetting the Bluetooth device by using a pin or wire in the tiny hole in the front of the device.

  5. Download all data (“Sample15”) since last site visit.

  6. Record most recent zero check value from the downloaded data.

  7. When calibration source reaches operating temperature (deltaT near 0), prepare to start the calibration sequence. Raise the zero-status flag (Zero_Status=True). Wait until the datalogger clock reaches a five-minute interval (e.g., 14:05, 10:20, 16:40). Turn the calibration source knob to ‘Stp’ and push in on the knob. The calibration sequence should start at 0 ppb. Sometimes the source will skip 0 and go to 200 ppb. If that is the case, briefly shut off the source, turn it back on, and select ‘Stp’ again.

  8. The calibration sequence takes 40 minutes to run, ten minutes each for four output levels (0, 200, 100, 50 ppb). When it is complete, the source pump will stop running. Download the calibration data (“Zero” or “ZSP” file). Lower the Zero_Status flag (Zero_Status=False).

  9. Shut off source, remove output line from filter inlet, remove source power leads, and store the source in transport case. Ensure that analyzer reading returns to ambient. Record the time in field notebook.

  10. Check for vacuum pressure at filter inlet.

  11. Remove Bluetooth serial adapter or USB cable and secure the equipment enclosure. Record departure time in field notebook.

Inlet Filter Cartridge Exchange (V5 sites)

Last updated September 20, 2024

Context: Semi-annual exchange of inlet filter cartridge (usually around April 1st and October 1st).

Tools and equipment needed: New filter cartridge, pliers, stepstool or short stepladder.

  1. Conduct all activities per usual site visit protocol.

  2. Place stepstool or stepladder so you have comfortable access to the inlet. It should look like this:

    An ozone filter connected to white plastic hoses and covered by a white PVC protective cap
    (USDA Forest Service photo)

  3. Pull the sample inlet line up, off the top of the filter cartridge:

    An ozone filter connected to white plastic hoses and covered by a white PVC protective cap. A red arrow points to a hand pulling up and removing one of the plastic tubes.
    (USDA Forest Service photo)

  4. Pull downward on the filter cartridge and T-connector to remove it from the inlet cap:

    An ozone filter connected to a white plastic tube and covered by a white PVC protective cap. A red arrow points to a hand pulling down and removing the filter from the plasctic cover.
    (USDA Forest Service photo)

  5. Remove the old filter cartridge from the connector. You may need to loosen the connector to do this.

    A ozone monitoring filter removed from a connecting plastic tube. A person's hand and two red arrows indicate to pull the filter from it's connection to the plasic tube.
    (USDA Forest Service photo)

  6. Install the new cartridge in the connector. Note the direction of the arrow on the cartridge’s sticker.

    A ozone monitoring filter being connected to plastic tubing. A person's hand and two red arrows indicate to push the filter into it's connection to the plasic tube.
    (USDA Forest Service photo)

  7. Tighten the connector, ensuring that the cartridge is inserted as far as possible into the connector.

    A person holding a pair of pliers to tighten a connection between an ozone filter and a plastic tube fitting.
    (USDA Forest Service photo)

  8. Press the cartridge firmly up into the cap.

    A person pressing an ozone filter cartridge into a plastic protective cup, with a red arrow indicating to press up.
    (USDA Forest Service photo)

  9. Replace the sample inlet line on top of the new filter. Ensure that the filter cartridge is inserted as far as possible into the connector. Temporarily loosen the connector if needed.

    A person's hand connecting a platic tube fitting to the top of an ozone filter.
    (USDA Forest Service photo)

  10. Tighten the sample inlet line connector with pliers. Check all other connections on the T-connector and sample inlet and calibration lines and tighten as needed.

    A person using a pair of pliers to tighten a connection between a plastic tube fitting and the top of an ozone filter.
    (USDA Forest Service photo)

  11. Check for vacuum pressure at the bottom of the T-connector. If vacuum pressure is weak or not present, re-check connections at the filter and at other connections at the connectors on the enclosure and at the lines inside the enclosure.

Instrument Exchange (Analyzer Only)

Last updated June 14, 2021

Context: Malfunctioning analyzer that cannot be field repaired

Tools and equipment needed: laptop with PC200W installed and USB/serial adapter; or Android smartphone with LoggerLink and Bluetooth connector, spare 2A fuse, inlet filter membrane.

  1. Download data with your laptop or phone per usual site-visit procedure.

  2. Identify instrumentation: top instrument (“Ozone Analyzer”) is the instrument to be removed. Bottom instrument (“Ozone Calibration Source”) is to remain in place. Leave all connections in place on the calibration source. Turn off the analyzer using the black rocker switch on the front of the instrument.

  3. Remove connections for power, air inlet, and data (RS-232 cable) from rear of analyzer, detach Velcro strap, and remove analyzer from enclosure. Leave the thermocouple (brown wire) in place if possible; it should be secured to the top of the calibration source with a piece of tape. If you remove it, remember to replace it before leaving.

    Ozone measuring instrument with a red arrow pointing to the rear of the instrument.
    (USDA Forest Service photo)

  4. Install the new analyzer and source in the enclosure using the Velcro strap. The analyzer must be placed on top of the source. Reinstall thermocouple (if you removed it previously) between the instruments before tightening the strap.

  5. Reattach the air inlet, data cable and power cord to the rear of the analyzer.

  6. Turn on the analyzer using the black rocker switch. If the analyzer does not immediately resume operation, check the fuses; it is easy to blow a fuse when re-attaching the power cord. Replace fuse if necessary.

  7. Check inlet line connections on the air solenoid located to the rear of the instruments; these connections can be easily dislodged during instrument handling. Ensure all lines attached to the solenoid are secure.

  8. Once instruments are installed and the analyzer is running, exchange the inlet filter membrane per usual site-visit procedure. Ensure vacuum is present at the inlet by briefly placing your finger over the inlet on the filter housing. If vacuum is not present, re-check inlet line connections.

  9. After the analyzer has been running for a few minutes, check ozone (20-80 ppb), flowrate (500-2500 cc/min), cell pressure (500-1000 mbar) and thermocouple (T_2B; 0-50 deg C) data on your laptop for reasonable values.

  10. Disconnect laptop or phone per usual site-visit procedure.

Instrument Exchange (Calibration Source Only)

Last updated January 8, 2024.

Context: Exchange of calibration source is required because of source malfunction or scheduled replacement with freshly calibrated instrument.

Tools and equipment needed: laptop with PC200W installed and USB/serial adapter; or Android smartphone with LoggerLink and Bluetooth connector, spare 2A fuse, flashlight or cellphone light.

  1. Download data with your laptop or phone per usual site-visit procedure. Remove insulation if it is installed.

  2. Identify instrumentation: top instrument (“Ozone Analyzer”) will remain in place. Bottom instrument (“Ozone Calibration Source”) is the instrument to be exchanged. Leave all connections in place on the ozone analyzer. Turn off the calibration source switch on the front of the instrument.

  3. Remove connections for power, air outlet, and data (RS-232 cable) from rear of calibration source, detach Velcro strap, and remove calibration source from enclosure. Support the analyzer if possible; avoid pulling or stretching the cables and air inlet at the rear of the analyzer. If necessary, temporarily detach the air inlet from the rear of the analyzer. Move the thermocouple (brown wire) out of the way.

    Ozone measuring instrument with a red arrow pointing to the rear of the instrument.
    (USDA Forest Service photo)

  4. Install the new calibration source in the enclosure using the Velcro strap. The calibration source must be placed underneath the analyzer. Place the thermocouple between the instruments (using a small piece of electrical tape if necessary) before tightening the strap.

  5. Reattach the air outlet, data cable and power cord to the rear of the calibration source. Reattach the air inlet to the analyzer, if you previously disconnected it.

  6. Turn on the calibration source’s power switch. The calibration source will probably not turn on; this is normal. Power to the calibration source is controlled by the datalogger. The source will turn on automatically at the next programmed calibration sequence, or when the datalogger enables cold-weather mode.

  7. Check inlet line connections on the air solenoid located to the rear of the instruments; these connections can be easily dislodged during instrument handling. Ensure all lines attached to the solenoid are secure.

  8. Check all three fuses; use flashlight if needed. Replace any that are blown.

  9. Reboot datalogger by unplugging the green power plug from the datalogger, waiting 10 seconds, and reinstalling the green plug. The analyzer should continue running. The calibration source may start up and go into cold-weather mode if the air temperature is low (below freezing).

  10. Once instruments are installed, ensure vacuum is present at the inlet by briefly placing your finger over the inlet on the filter housing. If vacuum is not present, re-check inlet line connections.

  11. Reinstall insulation if applicable. Disconnect laptop or phone per usual site-visit procedure.

RMRS Ozone Network Data Quality Assurance/Quality Control

Last updated September 30, 2024

Context: Annual collation and quality control of network data

Tools and equipment needed: none

Introduction: This document describes procedures for editing and quality control of data collected by the Rocky Mountain Research Station (RMRS) rural/high-elevation ozone monitoring network. This process is to take place annually after all data collection is terminated for seasonal sites, and after December 31st for sites that operate year-round.

Process Raw Data:

  1. Collate all files for a site, checking to see that duplicate records are deleted, and missing records are represented by a timestamp.

  2. Eliminate 15-minute data recorded during periodic calibration checks: Sort the collated raw data such that all records flagged as Zero_Status are at the top. Delete monitor data from these records.

  3. Delete data recorded during times when monitor was not running due to cold weather, insufficient battery power, etc. Search for NAN in data fields; delete ozone data for these records.

  4. Find erroneous data recorded when monitor and datalogger clocks were not in sync. These will be a few records every 7-15 days and may be identified by NAN in data fields and by improbably large ozone standard deviation (O3_Std) values.

  5. Sort data by descending ozone standard deviation (O3_Std) values. Delete ozone data where values exceed 9 ppb; high SD values indicate instrument malfunction.

  6. Examine average ozone (O3_Avg), sample flow (Flow_Avg) and sample cell pressure (Cell_Pres_Avg) for consistency; delete ozone data for records where malfunction is indicated.

  7. Record data completeness (number of records / total possible records)

Process Calibration Data:

  1. Open site calibration data file. Examine results for initial/final calibrator checks performed in the lab with NIST-traceable transfer standard. Create weekly calibrator output data by linear interpolation using initial/final check data.

  2. Examine weekly monitor calibration results page. Delete data where automated calibration checks failed or was not performed.

  3. Enter calibrator output data next to corresponding monitor calibration results.

  4. Generate file for entry to SAS regression analysis: Fields are timestamp (in Excel five-digit integer date), monitor cal check results, calibration output.

  5. Run SAS second-order regression script for this file. In output file, re-convert five-digit date stamps to regular dates. Save output file in calibration parameters directory.

  6. Examine RMSE in the output file: RMSE more than 2.0 indicates potentially invalid (non-linear) results. Delete if justified.

  7. Enter the three calibration parameters (Intercept, slope, square term) in the corresponding week on the calibration worksheet.

Adjust Ozone Data for Monitor Calibration Drift:

  1. Identify places in the collated sample file where valid calibration checks occurred. Enter the corresponding calibration parameters (b0, b1, b2). Generate values for the parameters for each individual 15-minute record by linear interpolation between valid cals. Then, generate values for adjusted ozone data (O3_Avg_Adj, O3_Max_Adj, O3_Min_Adj) by b0+(b1*x)+(b2*x2) where x is the ozone variable.

  2. Examine adjusted values graphically and calculate differences between raw and adjusted values. Deviation of more than 5 ppb should be re-examined for validity; delete suspect data.

Finalize Data:

  1. Ensure all data are sorted by ascending timestamp.

  2. Eliminate formulae in Excel cells by copy/paste values; save in Adjusted Data directory.

  3. Run SAS script to generate hourly ozone values, 8-hour running averages and daily-maxima values per EPA protocol; save in Adjusted Data directory.

  4. Run SAS script to generate annual 12-hour and 24-hour average ozone.

  5. Run SAS scripts to generate running three-month W126 values for 12-hour and 24-hour exposure; save output files in W126 directory.

  6. Run R script to generate AQS-compatible upload files.

  7. Extract daily maxima and fourth-maxima values and record in annual data spreadsheet.

Seasonal Site Closure Preparation

Last updated October 22, 2014

  1. Download data per usual site-visit procedure.

  2. Power-down datalogger by unplugging the green plug. Shut off analyzer and calibration source using the black rocker switches on the front of the instruments.

    Ozone measuring instrument with red arrows pointing to the front of the instrument.
    (USDA Forest Service photo)

  3. Remove connections for air inlet, serial cable and power from rear of analyzer and source and remove analyzer and source from enclosure.

    Ozone measuring instrument with four red arrows pointing to the rear of the instrument.
    (USDA Forest Service photo)

  4. Using a crescent wrench, detach the cables from the batteries. Use electrical tape to insulate each terminal as you remove the cable connection. Be careful not to short-circuit the battery terminals with either the cables or the wrench!

    Ozone measuring instrument with one red arrow pointing to a lose wire at the rear of the instrument.
    (USDA Forest Service photo)

  5. Using a Phillips (cross-tip) screwdriver, unscrew the terminal screws on the power controller for the solar panel and pull the connectors off. These are the two left-most terminals on the power controller. Be careful not to let the terminals touch each other. It may be necessary to completely unscrew the terminals. Insulate each connector individually with electrical tape.

    Ozone measuring instrument with two red arrows pointing to connectors on the side of the instrument.
    (USDA Forest Service photo)

  6. Secure all loose wires out of the way of the batteries and power controller; use tape if necessary. Close and latch the door of the enclosure.

  7. Check the hardware attaching the enclosure and solar panel(s) to the mount; use a crescent wrench to tighten any loose bolts or nuts