Measurement Devices. Topic 5 - Audio 56

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Brook Boone
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Topic 5 - Audio 56 Other Classifications Passive devices: Air diffuses in No power required for sampling Active devices: Requires power Pumps air through filter Key Points - Devices What lab sees:

1 Topic 5 - Audio 56 Other Classifications Passive devices: Air diffuses in No power required for sampling Active devices: Requires power Pumps air through filter Key Points - Devices What lab sees: Different devices measure different variables. All measure rate of decay-not mass or volume. Secular Equilibrium: When radon in equilibrium with decay products Takes four-hours in a closed container Rate of decay of radon decay products is limited to rate of decay of radon since it has a much longer half-life than its short-lived decay products. Knowing the rate of decay of decay products, one then also knows the rate of decay of radon. Time characteristics: Continuous: Provide concentrations over different time intervals (typically by hour) Building investigations Indication of tampering Can also provide average for deployment period Time Integrating: Provide a single average measurement for deployment period Do not provide hourly measurements. Grab samples: Snapshots in time Diagnostic or investigation applications Sampling time: minutes Should not be used for determining need for, or success of mitigation. 1

Topic 5 - Audio 57 Activated Charcoal Device: Samples: Results: Sampling times: Activated charcoal (AC) Radon pci/l Open face: 2-3 days (short term) Diffusion barrier: 2-7 days Follow laboratory

2 Topic 5 - Audio 57 Activated Charcoal Device: Samples: Results: Sampling times: Activated charcoal (AC) Radon pci/l Open face: 2-3 days (short term) Diffusion barrier: 2-7 days Follow laboratory recommendations Number for real estate test 2 QA/QC: Performance test required? Lab sees: Influences: Key use tips Advantages: Disadvantages: 10% duplicates, maximum 50/month 5% blanks, maximum 25/month 3% spikes minimum 3/year, maximum 6/month No, unless you are the lab analyzing device Gamma from Lead-214 & Bismuth-214 High moisture gain causes under-response, but lab can correct for this by weighing device. Air blown across device will cause over-response Cold room temperatures cause over response Hot room temperatures causes under response Biased towards conditions in latter part of exposure Do not deploy in extremely humid environments Do not deploy where air will blow on it Do not deploy on hot surfaces or in direct sunlight Do not change weight of device Advise lab if deployed in a cold or hot location Be accurate as to dates and times Get to lab within a week Simple and inexpensive Considerable experience with device Limited to short-term testing Does not provide hourly variations 2

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Topic 5 - Audio 64 Alpha Track Detectors Device Samples: Results: Sampling times: Alpha Track Detector (ATD) Radon pci/l 91 days to year (Long-term) Number for real estate test: 1 Used commonly for

4 Topic 5 - Audio 64 Alpha Track Detectors Device Samples: Results: Sampling times: Alpha Track Detector (ATD) Radon pci/l 91 days to year (Long-term) Number for real estate test: 1 Used commonly for post-purchase validation Used for follow-up measurements including post-mitigation testing QA/QC: Performance test required? Lab sees: Influences: Key use tips Advantages: Disadvantages: 10% duplicates, maximum 50/month 5% blanks, maximum 25/month 3% spikes minimum 3/year, maximum 6/month No, unless you are the lab analyzing device Alpha particles from radon that diffused in AND alpha from Polonium 214 and 218 produced from radon that entered device. Air blown across device can cause over-response Puncture in filter paper can cause over-response. Can pick-up radon if not stored properly Be accurate as to dates deployed Shut-Off device after test is done. Simple and inexpensive Considerable experience with device Used for long-term tests Limited to long-term testing Does not provide variations Precision can suffer if not exposed sufficient to radon (preferred minimum of 100 pci/l-days) 4

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Topic 5 - Audio 69 Electret Ion Chamber Device Samples: Results: Electret Ion Chamber (EIC) Radon pci/l (electret based ERPISU can also measure WL) Sampling times: Number for real estate test 2

6 Topic 5 - Audio 69 Electret Ion Chamber Device Samples: Results: Electret Ion Chamber (EIC) Radon pci/l (electret based ERPISU can also measure WL) Sampling times: Number for real estate test 2 QA/QC: Performance test required? Short-term (using S chambers and S-Electrets) Long-term (using L-chambers and L-Electrets) 10% duplicates, maximum 50/month 5% blanks, maximum 25/month 3% spikes minimum 3/year, maximum 6/month Reader calibrated once/year 5% set aside for voltage stability (should not exceed 1 volt/week for short-term or 1 volt /month for L electrets) Reference electret check of reader weekly Yes, unless a laboratory is reading voltages for you. Lab sees: Influences: Key use tips Advantages: Disadvantages: Radon enters device through diffusion filter. Radon and radon decay products break down. Alpha, beta & gamma causes ionization that changes charge on electret surface. External gamma can be accounted for Elevation can be accounted for Do not touch electret surface Keep electrets and chambers free of dust Keep reader in controlled environment Same reader used for several sampling devices Short-term and long-term Electrets can be reused until voltage drops to ~ 250V Does not provide variations over deployment period 6

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Topic 5 - Audio 75 Device Samples: Results: Sampling times: Number for real estate test Continuous Radon Monitors Continuous Radon Monitors (CRM) Radon pci/l Short-term 1 (provided measurements are

8 Topic 5 - Audio 75 Device Samples: Results: Sampling times: Number for real estate test Continuous Radon Monitors Continuous Radon Monitors (CRM) Radon pci/l Short-term 1 (provided measurements are in hourly increments) QA/QC: Annual calibration Annual background checks - scintillation style, once every 1,000 hrs 10% duplicates, with similar or like reading device Semi-annual cross-checks with recently calibrated device - Not required if check source available Routine instrument checks Air flow, (if applicable), batteries, etc. Performance test required? Lab sees: Yes No, if Blind Continuous Monitor where data sent to lab for report. Radon enters device and releases alpha which is detected and counted over time increments. Pulsed ion chamber (ion pulses) Silicon chip detector (electrical pulse) Scintillation cell (light flash) Influences: Key use tips Advantages: Disadvantages: Few, if placed per protocols Keep batteries charged Make results blind to occupant Provide hourly measurements Many also record temperature, movement, barometric pressure, etc. Can be expensive 8

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10 Topic 5 - Audio 80 Device Continuous Working Level Monitor Continuous Working Level Monitors (CWLM) Samples: Results: Sampling times: Number for real estate test QA/QC: Performance test required? Lab sees: Influences: Key use tips Advantages: Disadvantages: Radon decay products WL Short-term 1 (provided measurements are in hourly increments) Annual calibration Source check before each measurement New filter before each measurement 10% Duplicates if other CWLM or like device available Yes Radon and radon decay products are passed through a filter. Radon decay products adhere to filter. Alpha released from filter impacts detector. Impacts are counted over time increments. Measurement is a function of equilibrium factor Avoid location where air will blow directly on device. Regulate air flow carefully Avoid build up of dust on filter that would impede alpha particles from hitting detector (filter loading). Good idea to simultaneously deploy continuous radon measurement device. Provides hourly measurements Measures dose causing radon decay products Good for assessing benefit of air circulation and filters, especially in commercial buildings. Can be expensive 10

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12 Topic 5 - Audio 84 Device Samples: Results: Sampling times: Number for real estate test QA/QC: Performance test required? Lab Sees: Influences: Key use tips Advantages: Disadvantages: Electret Radon Progeny Integrating Sampling Unit Electret-Radon Progeny Integrating Sampling Unit (ERPISU) Radon Decay Products WL Short-term 2 (some devices have built in duplicate devices) Annual calibration New filter before each measurement 10% Duplicates if other CWLM or like measuring device available (note some units have two sampling units for 100% duplicates). No, if you are deploying device on behalf of certified lab No, if certified for electrets already but not developing reports. Yes, if you are analyzing and developing reports Radon and radon decay products pass through a filter. Radon decay products adhere to filter. Alpha released from filter enters electret chamber causing ionization. Radon decay products proportional to voltage drop, and air volume sampled. Measurement is a function of equilibrium factor Avoid location where air will blow directly on device. All factors that influence electrets (see section on EICs) Regulate air flow carefully Avoid build up of dust on filter that would impede alpha particles from hitting detector (filter loading). Good to simultaneously deploy with radon measurement device. Measures dose causing radon decay products. Uses same voltage reader as other electret devices. Assess benefit of air circulation/filters, especially commercial bldgs. Does not show hourly variations 12

Topic 5 - Audio 85 Key Points Grab Samples Grab Radon Collects known volume of air Scintillation cell or pulsed ion chamber detects alpha Sniff: sample measured directly after collection Very

13 Topic 5 - Audio 85 Key Points Grab Samples Grab Radon Collects known volume of air Scintillation cell or pulsed ion chamber detects alpha Sniff: sample measured directly after collection Very qualitative May be influenced by presence of Thoron (also an alpha emitter) Useful in finding areas of higher relative activities. Grab: Sample collected and held for four-hours before analyzing Allows for decay products to come into equilibrium Detects alphas from radon and Po-218 & Po-214 Very precise, but still limited to reporting levels at the time the sample was taken. Grab Working Level Measures radon decay products Collects volume of air through filter Filter removed and placed next to scintillation pad Alphas strike pad and release light Light measured by Photo Multiplier Tube and counted Times between sampling and successive measurements are critical Formula for calculating radon decay products is complex (see protocols if interested-but not a requirement to know formulas unless you plan to use these devices). No matter how accurate, no method that samples for less than 48-hours should be used for determining the need for mitigation. 13

14 Topic 5 - Audio 86 Significant Figures: Key Points Radon: Report to no more than one decimal place Examples: 3.1 pci/l - ok 3.11 pci/l - too many decimal places Radon Decay Products: Report to no more than three decimal places Examples: WL - ok WL - too many decimal places Standard Deviation: If lab reports one standard deviation: Example: 4.0 pci/l pci/l, means: 68% of theoretically similar measurements would be between 3.5 pci/l and 4.5 pci/l, or There is a 68% chance that the measured radon is between 3.5 and 4.5 pci/l. If lab reports two standard deviations Example: 4.0 pci/l pci/l, means 95% of theoretically similar measurements would be between 3.5pCi/L and 4.5 pci/l, or There is a 95% chance that the measured radon is between 3.5 and 4.5 pci/l. Report: Dates & times Locations Device ID Test conditions Concerns 14

Quality Assurance/ Quality Control. Topic 4 - Audio 46. Key Points

Quality Assurance/ Quality Control. Topic 4 - Audio 46. Key Points Topic 4 - Audio 46 Key Points : Measures taken to increase confidence in results. Quality Assurance: Program that assures that measures are being done and in a timely manner. Precision: How close measurements