1. What is Calibration? Tribal Air Monitoring Support Center, NAU
Radon Symposium
San Diego, California
September 21, 2016
Phillip H. Jenkins, PhD, CHP
Bowser-Morner, Inc.
Melinda Ronca-Battista
Tribal Air Monitoring Support Center, NAU

2. Who calibrates these? All of them have traceability to a standard.
We Take it For Granted
We so often assume that products we buy are “calibrated,” for example:
Thermometers
Odometers
Weights for shipping – lots of money involved
Who calibrates these? All of them have traceability to a standard.

3. Speedometer in Your Car
Your speedometer says you are going the speed limit.
The policeman says you are doing 80 in a 65.
One is right, one is wrong, but which one? Or maybe both are wrong?

4. Traceability: Every measurement depends on a “true” value
12/26/2017 7:40 AM
Traceability:
Every measurement depends on a “true” value
To design systems and to calibrate methods so they continue to measure “true”
Measurements trace their authority for the accuracy of their results to a calibration standard that is used as the “truth” that is used as a benchmark.
For example, you can buy a cylinder of CO2 from NIST at a known concentration for $3000.
Calibrate your scales at a weights and measures lab and receive a traceability certificate.
NIST’s statement on traceability is here:
Traceability is defined as an unbroken record of documentation ("documentation traceability") or an unbroken chain of measurements and associated uncertainties ("metrological traceability").
NIST SRMs are described on the NIST website as:
“Literally millions of measurements of elemental composition are performed each year worldwide. The vast majority of these measurements depend upon reference materials for establishing traceability. As a result, the quality of elemental determinations and comparability between laboratories are improved. “
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The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

5. Definition (Webster)
Calibrate - to standardize (as a measuring instrument) by determining the deviation from a standard so as to ascertain the proper correction factors.
In other words, making it work to measure correctly.
Will my thermometer measure 212 F in boiling water?

6. Calibration in the US
“Weights and Measures” labs use their “gold standard” devices to calibrate secondary devices.
These secondary standards are then used to calibrate devices/labs down the line, all the way to devices on the shelf but which do have NIST-traceability to a “gold standard” method in a long “chain of traceability.”
Without such traceability, we have no idea if 4 ounces measured on my postal scale is the same as that measured by UPS.
All measurement methods depend on traceability for their accuracy (except for “natural standards” like boiling and freezing).
From EPA transfer standard guidance: “gaseous ozone standards cannot be stored for any practical length of time due to the reactivity and instability of the gas. Therefore, ozone concentrations must be generated and verified” on site. When the monitor to be calibrated is located at a field monitoring site, it is necessary to use a transfer standard that is traceable to a more authoritative standard.
In cases when a standard, such as a cylinder of gas of known concentration, cannot be used, a standard method is established to transfer authority or traceability.
The ozone standard reference METHOD is established in 40 CFR Part 53 - AMBIENT AIR MONITORING REFERENCE AND EQUIVALENT METHODS
And the procedures for testing and establishing that method as a standard method is described in 40 CFR Part 53, Subpart B - Procedures for Testing Performance Characteristics of Automated Methods for SO2, CO, O3, and NO2.

7. Calibration for radon and other gasses:
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Calibration for radon and other gasses:
Radon, like ozone, is unstable and needs to be generated as-needed to calibrate all device types.
Other gasses, like SO2, have known-concentration cylinders that can be purchased to calibrate SO2 detectors, but no similar system is possible for radon or ozone.
In these cases, calibration requires making a known concentration of the gas:
Radium-226 sources emit radon gas atoms at a known rate dependent on the # of curies in the source.
These radon atoms are then mixed with an accurately-known volume of air to produce a “true” concentration of radon.
This “true” concentration is then used to calibrate all device types, so that whatever signal is produced by the device can be converted to pCi/L.
© 2007 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

9. Ra-226 SRM with NIST certificate at NAREL
12/26/2017 7:40 AM
NIST SRM radium-226 sources emit radon-222 gas atoms at a known rate dependent on the # of curies in the SRM.
The “perfectly known” # of radon atoms are then mixed with an extremely accurately known volume of air to produce a “true” pCi/L concentration.
The LV chamber used the following method to generate known Rn concentrations (and see the attached pdf for the full scheme) with small and well-documented uncertainties:
Steps to Generating a Standard Test Atmosphere for Radon During an Exposure Period:
1. An original NIST SRM 226Ra in solution
2. Generation of seven 226Ra laboratory standards, with five designated as working standards routinely used to generate 222Rn, one laboratory standard held in reserve, and one laboratory standard sent to NIST for performance evaluation (five bubblers used routinely, #3 held in reserve, and sent to NIST in flame-sealed ampoule for performance evaluation)
3. Ingrowth of 222Rn gas from the decay of the 226Ra in one of the working standards during a 30 day regeneration period (each of the five working standards is used in rotation, and are used for other purposes including performance evaluations so that each standard is used approximately once every six months),
4. The volumetric transfer of at least 8-9 liters of air containing the 222Rn gas from a working standard, into an evacuated Tedlar bag, which is used to fill:
5. Transfer of gas from bag to the Lucas-type scintillation cells used six at a time, and rotated from a stock of 37
6. Generation of individual calibration factors (CFs) for these six Lucas-type cells based upon the known 222Rn concentration transferred into each Lucas-type cell from the bag
7. Use of between two and four Lucas-type scintillation cells to perform simultaneous grab measurements of 222Rn in the chamber. The average of these grab samples counted in these just-calibrated Lucas cells form the primary measurement standard for the 222Rn in this laboratory
8. Comparison of the radon chamber concentration at that time with the counts produced by each flow-through scintillating alpha counter (SAC) to generate individual CFs for each flow-through SAC
9. The use of the mean of between two and four SACs to produce a value for the integrated 222Rn concentration in the chamber during the exposure period typically ranging from 24 to 96 hours.
Ra-226 SRM with NIST certificate at NAREL
© 2007 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

10. Radon, like All Measurements:
Require periodic recalibrations—radon measurement systems require exposure in a radon chamber in controlled, monitored and documented conditions.
Your QC checks verify continued stable operation, but all device types require some recalibration:
Calibrating weird things at a NIST lab

11. How We Got To Now
In the 1980’s, at the time of the inception of the National Radon Proficiency Program (NRPP) there were several radon labs with chambers within the federal government:
DOE – EML, Mound, Grand Junction, ORNL, Lawrence Berkeley
EPA – Montgomery, Las Vegas
Bureau of Mines, Denver

12. How We Got To Now
The government labs had well-trained personnel and a good system of intercomparisons among themselves and internationally.
In the early days of the NRPP, the radon reference and calibration were not the top priorities, so these were not covered in the original protocols.

13. How We Got To Now Fast forward to 2016:
All of the aforementioned government chamber labs are (essentially) gone.
The reference has been based on transfer from a liquid standard containing radium.
This standard was at EPA Las Vegas, now being transitioned to Montgomery.

14. Fast forward to 2016:
There is no definition of calibration in standards or qualifications of laboratories and personnel performing calibrations—soon to be codified in the MS-QA standard.
There is no formal program of intercomparisons among laboratories within the US or US involvement with international intercomparisons, but plans are underway.

15. AARST/ANSI Standards An AARST/ANSI standard is in process now: MS-QA.
This standard will define in a consensus standard the QA required for radon testers and laboratories, including calibration for all device types.

16. Radon Measurement Devices
Good news and bad news: there are many ways to measure radon.
Each method and particular device type have different considerations regarding calibration.

17. Calibrating Continuous Radon Monitors
Internal Checks, battery replacements
Background assessments
If PMT, then plateau
Calibration factor, exposure in chamber
Calibration statement and sticker
If entity other than manufacturer, training and authorization from manufacturer must be obtained.

18. Calibrating Charcoal-Based Measurement Systems
Exposures in chamber are required for different:
Exposure times-maximum and minimum
Range of relative humidities
Temperatures
Develop calibration curves/equations, for each charcoal type
Expensive and time consuming

19. Calibrating Alpha Track Measurement Systems
Manufacturer is usually also the laboratory
Exposures in chamber of representative number of devices from each sheet of material
Blanks from each sheet of material

20. Calibrating Electret Ion Chamber Measurement Systems
Manufacturer may also be the laboratory
Stability of the electret must be verified
Exposures in chamber
Response to gamma must be quantified
Calibration equations established

21. Calibrations are necessary, and their QA requirements will be listed in MS-QA:
Thank you for your work, and us with questions: Dr. Phil Jenkins, Melinda Ronca-Battista