Lesson 5

1. Lesson 5 What devices do we use to measure radon?

2. Short-term test 2 to 90 days Long-term test 91 to 365 days How long will the test last? Advantage • Provides quick answer Disadvantage • Does not account for radon variations from day to day or season to season Used for most real estate transactions Advantage • Provides more information about year-round average radon level Disadvantages • Takes longer to get results • Residents forget test is running

3. Time-integrated sampling Average concentration over a period of time Period may range from a few days (for most home inspections) to a year or more Continuous sampling Automatic sampling over set intervals of time 3. Grab sampling Quick snapshot at a moment in time Cannot be used in home inspections Advantages Can collect several samples in one day Can observe conditions while sampling Disadvantages Not certain how well it correlates with long-term integrated measurement Requires additional training and expensive equipment Sampling methods for radon and radon decay products

4. Would you use a grab sample to determine whether a home needs radon mitigation? Why or why not? No, because It provides only a snapshot or radon at brief moment in time We don’t know how well it correlates with longer-term measurements Decision about mitigation should be based on averages over longer periods of time EPA does not recommend use of grab samples for pre-mitigation or post-mitigation testing or for follow-up measurements Grab sample

5. Questions? • About sampling methods

6. Standards for devices All devices must meet the requirements of the National Environmental Health Association (NEHA) or the National Radon Safety Board (NRSB) Read and follow the directions of the manufacturer of the device you use

7. Passive devices Do not require power (electricity or batteries) to operate Less expensive Used in most real estate transactions Active devices Require power to operate More expensive Require calibration Types of devices

8. Types of passive devices • Activated charcoal adsorption • Charcoal liquid scintillation • Electret ion chamber (electrostatic radon monitor) • Alpha track detector

9. Passive devicesActivated charcoal adsorption Use for short-term tests • Airtight canister that contains granular activated carbon is opened • Radon from surrounding air enters canister and is adsorbed (held on its surface) by charcoal • At end of test period, canister is sealed and sent to approved lab for analysis • Two types • Open face • Diffusion barrier • (filter over face)

10. Advantages Requires no external power Inexpensive Easy to place Simple to use Easy to mail to lab Measures over short time periods Disadvantages Biased toward end of sampling period Works best for short sampling periods May be affected by sampling conditions (temperature, humidity, and drafts) Sampling conditions during test period may be unknown Must be analyzed by approved lab soon after test period Difficult to know if device has been tampered with Passive devicesActivated charcoal adsorption

11. Passive devices:Charcoal liquid scintillation Use for short-term tests • Small vial containing activated charcoal is opened • Radon from surrounding air enters vial and is adsorbed by charcoal • At end of test period, vial is sealed and sent to approved lab for analysis

12. Advantages Same as for activated charcoal adsorption canister Disadvantages Same as for activated charcoal adsorption canister Especially: device must be analyzed by approved lab soon after test period Passive devicesCharcoal liquid scintillation

13. Passive devicesElectret ion chamber • Most common: electret-passive environmental radon monitor (E-PERM) • Use for short-term and long-term tests

14. Passive devicesElectret ion chamber • Electrostatically charged disk (electret) is placed in small chamber • Radon diffuses into chamber and emits alpha particles during decay • Alpha particles ionize the air molecules • Ions move to charged surface of electret, thus reducing its initial charge • Voltage meter measures initial and final voltages • Rate of change of charge is proportional to concentration of radon in air

15. Advantages Requires no external power Provides true time-integrated measurements Each electret may be reused many times Can provide immediate results Disadvantages Requires additional training to use Must measure and correct for background gamma radiation May be affected by high humidity and dust Temperature differences between initial and the final voltage readings may cause errors Does not provide evidence of tampering Passive devicesElectret ion chamber

16. Passive devicesAlpha track detector Use for long-term tests only • Contains piece of film or plastic that records impacts (tracks) of alpha particles produced by decay of radon and its decay products • At end of test period, detector is returned to approved lab • Lab counts alpha tracks on film and computes radon concentration

17. Advantages Requires no external power Inexpensive Simple to use Easy to mail Provides true time-integrated measurements Not biased toward most recent exposure Can measure over long periods (90-365 days) Disadvantages Cannot measure for short time periods May not provide precise measurement when concentrations are low May be affected by sampling conditions Sampling conditions during test period may be unknown Passive devicesAlpha track detector

18. Questions? • About passive measurement devices

19. ActivityHandout 5-1A

20. Active devices • Electronic devices • Require power (batteries or electricity) to operate • Measure and record amount of radon or its decay products in air at regular intervals • At least once an hour • Results are average of these readings • Can show changes in radon levels during test period

21. Active devices • Use for short-term tests • Air either diffuses or is pumped into a counting chamber Continuous radon monitor Continuous working level monitor

22. Advantages Provide results on-site Can track real-time variations in radon concentrations Can measure various time intervals Some models record temperature, humidity, barometric pressure, movement, and other environmental factors Can indicate tampering Disadvantages Require power to operate More expensive Must be calibrated regularly Require additional training to operate Some are sensitive to humidity Some are heavy and bulky Active devicesContinuousradonmonitors

23. Questions? • About active radon measurement devices

24. Short-term test How many days? 2-90 Advantage? Provides a quick answer about radon levels Disadvantage? Does not account for radon variations from day to day or season to season Long-term test How many days? 91-365 Advantage? Gives more information about year-round average radon levels Disadvantage? Takes longer to get results SummaryLength of tests

25. SummarySampling methods • Time-integrated sampling • Continuous sampling • Grab sampling Which methods should home inspectors use? Time-integrated and continuous sampling

26. Passive Activated charcoal adsorption Charcoal liquid scintillation Electret ion chamber (electrostatic radon monitor) Alpha track detector Active Continuous radon monitors Continuous working level monitors SummaryTypes of devices

27. Questions?

28. Checkyour understanding • See handout 5-2