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Lesson 8
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  1. Lesson 8 How can you provide quality assurance and quality control?

  2. QA/QC in radon measurement • Activities to make sure that radon testing equipment and services meet EPA quality standards • Goal: to reduce or eliminate errors • Helps clients make well-informed decisions that affect • Health • Finances

  3. QA/QC components • Measuring to assess • Precision • Accuracy • Checking and documenting performance of devices

  4. Precision Are measurements repeatable or consistent when an identical item is measured several times? Measurements are precise (close together) but not accurate (not near bull’s eye)

  5. Accuracy Are measurements close to the correct or true value? Measurements are accurate (in bull’s eye) but not precise (close together)

  6. Precise Measurements are close together Accurate Measurements are in bull’s eye Precise and accurate

  7. Tests for passive devices • Duplicates • Measure precision • Spikes • Measure accuracy • Blanks • Measure bias (how far measurements are from accurate)

  8. Make duplicates at least 10% of total number of measurements Set out two identical devices that have been stored in the same place Place side by side, about 4 inches apart Leave in place for the same amount of time Label them so that You know they are duplicates Lab will not know they are duplicates Ship devices to the lab together Duplicates(measure precision)

  9. Check duplicate results

  10. Check RPD(relative percent difference) If average of 2 results is 4 pCi/L or more, • RPD should be no more than 25% • If RPD is greater than 25%, investigate

  11. Spikes(measure accuracy) • Make spikes (spiked samples) • At least 3% of total measurements or • At least 3 per year • No more than 6 per month • Send unexposed device to QA/QC lab where it will be exposed to known radon concentration • Label device so that • You know it is a spike • Lab will not know it is a spike • Ship exposed device to analytical lab

  12. Check spike results For spikes at 4 pCi/L or higher, calculated value should be no more than 0.10 If result is higher, investigate

  13. Blanks(measure bias) • Check accuracy by measuring bias • How close is measured value to target value? • Help determine whether accuracy has been affected in • Manufacturing • Shipping • Storing • Processing the device

  14. Blanks • Make blanks at least 5% of total number of measurements • Unwrap a device but do not open it. • Leave unopened device in place for standard exposure period • Label device so that • You know it is a blank • Lab will not know it is a blank • Ship unexposed device to lab

  15. Blanks • In theory, blanks should measure 0 pCi/L • In practice, blanks should measure at lower limit that device can measure • If result is higher, investigate

  16. Active devices • Calibrate at least once a year (or as manufacturer suggests) • Check device manual or ask manufacturer for referral to calibration lab

  17. Routine instrument checks • Check equipment periodically • Include all components • Batteries • Pumps • Electronics • Airflow

  18. Information about device Manufacturer Type/model Serial or ID number Times Start date and time Stop date and time Exact location of device on diagram of room and building Other building information Type of building Type of heating system Foundation types Operation of humidifiers, air filters, electrostatic precipitators, and clothes dryers Test conditions Document all tests

  19. Document your QA/QC activities • QA/QC plan from any lab you use • Information about device • Manufacturer • Type/model • Serial or ID number • For passive devices • Test dates and times • Percentage of tests in relation to total tests • Label used to identify QA/QC test • Type of QA/QC measurement • Duplicates • Spikes • Blanks • For active devices • Calibration dates and other details

  20. Note on quality of information • Even with good QC/QA, data quality if limited • Test is out of your control when it is left unattended • Important to inform residents of necessary test conditions and persuade them to maintain conditions • Important to be alert to possible interference

  21. SummaryQA/QC for passive devices See handout 8-1

  22. SummaryActive devices • Calibrate at least once a year

  23. SummaryAll devices • Check all instruments periodically • Document all measurements • Document all QA/QC activities

  24. Questions?

  25. Checkyour understanding • See handout 8-2