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

Slide 8-1 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

Slide 8-2 QA/QC components Measuring to assess –Precision –Accuracy Checking and documenting performance of devices

Slide 8-3 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)

Slide 8-4 Accuracy Are measurements close to the correct or true value? Measurements are accurate (in bull’s eye) but not precise (close together)

Slide 8-5 Precise and accurate Precise Measurements are close together Accurate Measurements are in bull’s eye

Slide 8-6 Tests for passive devices Duplicates –Measure precision Spikes –Measure accuracy Blanks –Measure bias (how far measurements are from accurate)

Slide 8-7 Duplicates (measure precision) 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

Slide 8-8 Check duplicate results StepHow to calculateExample 1 Calculate average of two results Average = Result 1 + Result = Calculate relative percent difference (RPD) of two results RPD = (Result 1 – Result 2) x 100 Average of two results ( ) x 100 = x 100 = %

Slide 8-9 Check 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

Slide 8-10 Spikes (measure accuracy) Make spikes –At least 3% of total measurements or –At least 3 per year –No more than 6 per month Send unexposed device to special 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 regular lab

Slide 8-11 Check spike results How to calculateExample Compare target value and measured value Target value–Measured value Target value 5.7 – 5.2 = For spikes at 4 pCi/L or higher, calculated value should be no more than 0.10 If result is higher, investigate

Slide 8-12 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

Slide 8-13 Blanks Label device so that –You know it is a blank –Lab will not know it is a blank Ship unexposed device to lab 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

Slide 8-14 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

Slide 8-15 Active devices Calibrate at least once a year Check device manual or ask manufacturer for referral to calibration lab

Slide 8-16 Routine instrument checks Check equipment periodically Include all components –Batteries –Pumps –Electronics –Airflow

Slide 8-17 Document all tests 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

Slide 8-18 Document your QA/QC activities QA/QC plan from any lab you use 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 Information about device –Manufacturer –Type/model –Serial or ID number

Slide 8-19 Questions?

Slide 8-20 Summary QA/QC for passive devices Type of test Measures% of total measurements DuplicatePrecisionAt least 10% SpikeAccuracyAt least 3% BlankBias/accuracyAt least 5%

Slide 8-21 Summary Active devices Calibrate at least once a year

Slide 8-22 Summary All devices Check all instruments periodically Document all measurements Document all QA/QC activities