Measuring radon in residential properties
Lesson 5:
What devices do we use to measure radon?
What devices do we use to measure radon?
Lesson overview This lesson introduces the various types of devices that we use to measure radon. Lesson objectives By the end of this lesson, the learners will be able to: · Identify the durations of the two types of radon testing · List the three basic methods for sampling radon and radon decay products · Name the two types of devices that we use to measure radon for home inspections · Identify four types of passive radon devices · Describe the advantages and disadvantages of the four types of passive devices · Name two types of active devices Introduce the lesson. See slide 50.
In this lesson, we are going to talk about the various devices that we use to measure radon. As we noted at the beginning of this training, you cannot see, smell, or taste radon, so you need special equipment to detect it. See slide 51.
Tests can be shortterm (lasting 2 to 90 days) or longterm (91 days to a year). The advantage of shortterm testing, of course, is that you can get answers quickly. However, shortterm testing does not show radon variations from day to day and season to season, so you do not get as much information about the yearround average radon level. But for most real estate transactions, home inspectors use shortterm tests. Longterm tests last more than 90 days. They provide more information about a home’s yearround average radon level. However, since they take longer to get results, they are used less commonly for real estate transactions and home inspections.
Lesson 51
Notes
Measuring radon in residential properties
What devices do we use to measure radon?
Notes
See slide 52.
Before we get to the devices themselves, we should explain the three basic methods for sampling radon and radon decay products: · Timeintegrated sampling · Continuous sampling · Grab sampling First, we’ll consider timeintegrated sampling. Because the concentrations of radon and its decay products vary over time, we often seek an average concentration over a period of time. This period may range from a few days to a year or more, although home inspectors usually sample for the shorter end of the range. The devices that sample concentrations over such periods and average the results are called timeintegrating detectors. The second method is continuous sampling. Continuous devices automatically sample at set intervals (such as every hour). They measure the variation in radon and radon decay products, showing the concentration varies throughout the measurement interval. The third method is grab sampling. It involves collecting a representative air sample from the home over a short period of time—such as a few minutes. It is a quick snapshot of the level or radon or radon decay products in the home at the moment of sampling. A grab sample gives speedy results, and samples can be analyzed either in a laboratory or with portable equipment. A tester could collect several samples in a single day and could observe the conditions while sampling the air. However, we don’t know how well a grab sample measurement correlates with a longterm integrated measurement. In addition, the equipment is expensive and requires skilled technicians to operate, so home inspectors would rarely use grab samples. See slide 53. Consider.
Would you use a grab sample to determine whether a home needs radon mitigation? Why or why not?
Lesson 52
Measuring radon in residential properties
What devices do we use to measure radon?
Correct answer: No. A grab sample provides only a snapshot of radon at a brief moment in time. We don’t know how well it correlates with longerterm measurements. A decision about mitigation should be based on averages over longer periods of time. The EPA does not recommend the use of grab samples for premitigation or postmitigation testing or for followup measurements. See slide 54. Consider.
Do you have any questions about these methods so far? See slide 55.
Now we can talk about the radon measurement devices themselves. First, we should emphasize that all devices must be listed by the National Radon Safety Board (NRSB) or the National Environmental Health Association (NEHA). Second, note that many manufacturers make various radon devices. There are sometimes slight differences in how to use these devices. We’ll discuss the general principles, but you must read and follow the directions for the particular device that you use. See slide 56.
There are two types of radon measurement devices: · Passive devices do not require power (electricity or batteries) to operate. Passive devices are generally less expensive and are used in most real estate transactions, which is when most home inspectors conduct radon measurements. · Active devices do require power to operate. They are generally more expensive than passive devices and are less often used by home inspectors. See slide 57.
Since you will probably use passive devices most often, we’ll concentrate on them. Four types of passive devices are commonly used: · Activated charcoal adsorption
Lesson 53
Notes
Measuring radon in residential properties
What devices do we use to measure radon?
· Charcoal liquid scintillation · Electret ion chamber · Alpha track detector
Notes
See slide 58.
The first passive device, the activated charcoal adsorption device, is used for shortterm tests (often 2 to 7 days). There are two types of activated charcoal adsorption devices: · Open face · Diffusion barrier, which has a filter over the face The charcoal adsorption device consists of an airtight canister that contains granular activated carbon. When the canister is opened, radon from the surrounding air enters the canister and is adsorbed by the charcoal (that is, the charcoal holds the radon on its surface). At the end of the test period, the canister is sealed and promptly sent for analysis to a laboratory listed by NEHA or the NRSB. The lab counts the gamma decay from the adsorbed radon and calculates the radon in the home. See slide 59.
As you can imagine, each device has certain advantages and disadvantages. The advantages of the activated charcoal adsorption device are that it • Requires no external power • Is inexpensive • Is easy to install • Is simple to use • Is easy to mail to a lab for analysis • Measures over short time periods The disadvantages of an activated charcoal adsorption device are that it • Is biased toward readings from the end of the sampling period • Works best for short sampling periods • May be affected by sampling conditions (temperature, humidity, and drafts), and the sampling conditions during test period may be unknown • Must be analyzed by approved laboratory soon after the testing period Lesson 54
Measuring radon in residential properties
What devices do we use to measure radon?
It is also difficult to know if device has been tampered with, which may be a concern in real estate transactions. See slide 510.
The second passive device, the charcoal liquid scintillation device, is similar. It too is used for shortterm tests (usually 27 days). The device consists of a small vial that contains activated charcoal. When the vial is opened, radon from the surrounding air enters the vial and is adsorbed by the charcoal. At the end of the test period, the vial is sealed and sent to an EPA approved laboratory for analysis. See slide 511.
The advantages and disadvantages of a charcoal liquid scintillation device are similar to those of the activated charcoal adsorption device. However, because the liquid scintillation device uses much less charcoal, it must be analyzed very quickly after the measurement period ends. See slide 512.
The third passive device is the electret ion chamber. The most common electret ion chamber is called an EPERM (electretpassive environmental radon monitor). It is used for either shortterm or longterm tests. This device detects ions that are produced by the decay of radon. Ions are electrically charged particles produced when atoms or molecules gain or lose electrons. See slide 513.
With an EPERM test, an electrostatically charged disk (electret) is placed in a small container (an ion chamber). • Radon diffuses into the chamber and emits alpha particles during decay. • Alpha particles ionize the air molecules in the chamber. That is, the alpha particles cause the air molecules to gain or lose electrons, thus giving the air molecules electrical charges.
Lesson 55
Notes
Measuring radon in residential properties
What devices do we use to measure radon?
• The electrically charged molecules (ions) move to the charged surface of the electret, thus reducing its initial charge. • A voltage meter measures the initial and the final voltages. • The rate of change of the charge is proportional to the concentration of radon in the air. See slide 514.
The electret ion chamber also has advantages and disadvantages. The advantages of the electret ion chamber are the following: • It requires no external power. • It provides true timeintegrated (average) measurements. • Each electret may be reused many times. • It can provide immediate results. However, the electret ion chamber also has disadvantages: • It requires significant additional training to use. • The technician must measure and correct for background gamma radiation. • The device may be affected by high humidity and dust. • Temperature differences between the initial and the final voltage readings may cause slight errors. • It does not provide evidence of tampering. See slide 515.
The fourth passive device is the alpha track detector. It is used for longterm tests only. The alpha track detector contains a piece of film or plastic that records the impacts (tracks) of alpha particles produced by the decay of radon and its decay products. At the end of the test period, the detector is sent to an approved lab. The lab counts the alpha tracks on the film and computes the radon concentration. See slide 516.
The advantages of the alpha track detector are that it • Requires no external power • Is inexpensive • Is simple to use • Is easy to mail
Lesson 56
Notes
Measuring radon in residential properties
What devices do we use to measure radon?
• Provides true timeintegrated (average) measurements • Is not biased toward the most recent exposure • Can measure over long periods The disadvantages of the alpha track detector are that it • Cannot measure for short time periods • May not provide precise measurement when concentrations are low • May be affected by sampling conditions • Sampling conditions during the test period may be unknown See slide 517. Consider.
What questions do you have about passive devices? See slide 518. See Handout 51A.
Handout 51 contains a list of passive devices and blank columns for the lengths of tests for which they are used and for their advantages and disadvantages. Fill in as many of the blanks as possible. When you have finished, review the completed sheet (Handout 5 2B). You can compare your answers with those in the completed form. See Handout 51B with the correct answers. See slide 519.
We’ve talked about passive devices in some detail. As we noted earlier, most home inspectors who are working on real estate transactions use passive devices. We’ll just briefly mention the other type of devices: active devices: · Active devices are electronic devices that do require power to operate. · They continuously measure and record the amount of radon or its decay products in the air. · They record the measurements at regular intervals (at least once an hour) · They can show rises and falls in the radon level during the test period.
Lesson 57
Notes
Measuring radon in residential properties
What devices do we use to measure radon?
See slide 520.
Notes
Active devices include · Continuous radon monitors · Continuous working level monitors, which measure radon decay products Continuous monitors are used for shortterm tests. In a continuous monitor, air either diffuses or is pumped into a counting chamber. The device records measurements at regular intervals (every hour or more often). The results are an average of these periodic readings. See slide 521.
Continuous radon monitors offer several advantages. They • Provide results onsite • Give precise, accurate results • Can track realtime variations in radon concentrations • Can measure various time intervals • Some models record temperature, humidity, barometric pressure, movement, and other environmental factors • Can provide evidence of tampering The disadvantages of the continuous radon monitor are that they • Require power to operate • Are more expensive • Must be calibrated regularly • Require additional training to operate In addition, • Some are sensitive to humidity • Some are heavy and bulky See slide 522. Consider.
What questions do you have about active radon measurement devices? See slide 523.
Lesson 58
Measuring radon in residential properties
What devices do we use to measure radon?
In this lesson, we focused on the various types of devices that you can use to measure radon, although we talked a bit about testing protocols. For example, we explained that tests can be short term or long term. Consider.
Do you remember how long a shortterm test lasts? Correct answer: 2 to 90 days. Consider.
Do you recall the advantage and disadvantage of shortterm tests? Correct answer: Advantage: Provides a quick answer about radon levels. Disadvantage: Does not account for radon variations from day to day or season to season. Consider.
What is the duration of a longterm test? Correct answer: 91 to 365 days Consider.
What is the advantage and what is the disadvantage of a longterm test? Correct answer: Advantage: Gives more information about yearround average radon levels. Disadvantage: Takes longer to get results See slide 524. Explain.
We also mentioned three sampling methods for radon and radon decay products: • Timeintegrated sampling • Grab sampling • Continuous sampling
Lesson 59
Notes
Measuring radon in residential properties
What devices do we use to measure radon?
Notes
Consider.
Do you recall which method home inspectors most commonly use and why? Correct answer: Timeintegrated sampling is most commonly used because it provides quick, accurate answers, which are important for real estate transactions. See slide 525.
We identified two types of devices: • Passive • Active Consider.
Of these, which types of devices do home inspectors most commonly use? Correct answer: Passive
We identified four types of passive devices, with their advantages and disadvantages: • Activated charcoal adsorption • Charcoal liquid scintillation • Electret ion chamber (electrostatic radon monitor) • Alpha track detector Finally, we talked briefly about two types of active devices: • Continuous radon monitors • Continuous working level monitors See slide 526. Consider.
Do you have any questions about radon measurement devices? See slide 527. Check comprehension. See Handout 52A. This comprehension check is not graded.
Lesson 510
Measuring radon in residential properties
What devices do we use to measure radon?
Now you’re going to see whether you remember the main points that we’ve discussed in this lesson. Please answer the questions on handout 53A. When you all finish, we’ll review the answers together. Review the answers. See Handout 52B, the answer key. See Handout 53, the lesson summary sheet.
Lesson 511
Notes
Measuring radon in residential properties
What devices do we use to measure radon?
Resources
Notes
U.S. Environmental Protection Agency. Indoor Air—Radon. 2005. “Indoor Radon and Radon Decay Product Measurement Device Protocols.” www.epa.gov/cgibin/epaprintonly.cgi., accessed June 21, 2006. ———. A Citizen’s Guide to Radon: The Guide to Protecting Yourself and Your Family from Radon. U.S. EPA 402K02 0006. September. www.epa.gov/radon/pubs/citguide.html.
Lesson 512
Measuring radon in residential properties
What devices do we use to measure radon?
Handout 51A: Passive measurement devices Work with a partner or other learners to fill in this chart. Type of device
Length of test
Advantages
Activated charcoal adsorption
Charcoal liquid scintillation
Electret ion chamber
Alpha track detector
Lesson 513
Disadvantages
Measuring radon in residential properties
What devices do we use to measure radon?
Handout 51B: Passive measurement devices Answer key Type of device Activated charcoal adsorption
Length of test
Advantages
Shortterm tests • Requires no external power • Inexpensive • Easy to install • Simple to use • Easy to mail to lab • Measures over short time periods
Charcoal Shortterm tests • liquid scintillation • • • •
Requires no external power Inexpensive Easy to install Simple to use Easy to mail to lab • Measures over short time periods
Lesson 514
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 laboratory soon after the testing period • Difficult to know if device has been tampered with • 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 laboratory soon after the testing period • Difficult to know if device has been tampered with • The device uses much less charcoal, so it must
Measuring radon in residential properties
Type of device
Length of test
What devices do we use to measure radon?
Advantages
Disadvantages be analyzed very soon after the sample period is completed
Electret ion chamber
Shortterm and • Requires no longterm tests external power • Provides true timeintegrated measurements • Each electret may be reused many times • Can provide immediate results
Alpha track detector
Longterm tests • Requires no external power • Inexpensive • Simple to use • Easy to mail • Provides true timeintegrated measurements • Not biased toward most recent exposure • Can measure over long periods (91365 days)
Lesson 515
• Requires training to use • Must measure and correct for background gamma radiation • May be affected by high humidity • Temperature differences between initial and the final voltage readings may cause errors • Does not provide evidence of tampering • Cannot measure for short time periods unless radon concentrations are high • May not provide precise measurement when concentrations are low • May be affected by sampling conditions • Sampling conditions during test period may be unknown
Measuring radon in residential properties
What devices do we use to measure radon?
Handout 52A: Check your understanding Select the best answer from the choices below. Circle the correct answer. 1. A longterm radon test a. Is most commonly used for real estate transactions b. Is useful to provide a snapshot of radon activity at a brief moment c. Gives information about a home’s yearround average radon levels d. Lasts 47 days
apply to an activated charcoal adsorption device: a. It is easy to install. b. It is simple to use. c. It is expensive. d. It measures radon over short time periods.
2. Timeintegrated sampling a. Provides the average concentration over a period of time b. Provides the median radon level over a period of time c. Provides a snapshot radon level for a moment in time d. Correlates the radon level in outside air in relation with the indoor level 3. A passive device a. Requires batteries or electricity to operate b. Does not require power to operate c. Does not react to radon or its decay products d. Submits to authority without question 4. One of the following is not a passive radon device: a. Activated charcoal adsorption b. Charcoal liquid scintillation c. Electret ion chamber d. Continuous working level monitor
6. A charcoal liquid scintillation device has the following disadvantage: a. It must be analyzed very quickly after the measurement period ends. b. It requires significant training to use. c. It must be corrected for background gamma radiation. d. It cannot measure for short time periods unless radon concentrations are high. 7. An electret ion chamber measures a. Voltage changes resulting from ions created by radon decay b. The number of ion tracks on a piece of film or plastic c. The adsorption of radon onto an electrically charged disk d. The adsorption of radon into charcoal ions 8. An EPERM device a. Operates well in high humidity b. Is accurate under all temperature conditions c. Requires significant training to use d. Requires external power
5. One of the following features does not
Lesson 516
Measuring radon in residential properties
9. An alpha track detector a. Is expensive b. Is difficult to use c. Does not provide true time integrated measurements d. Is not biased toward most recent exposure
What devices do we use to measure radon?
10. Active devices a. Record measurements once a day b. Work on solar power c. Can show changes in radon levels during the test period d. Are inexpensive
Lesson 517
Measuring radon in residential properties
What devices do we use to measure radon?
Handout 52B: Check your understanding Answer key The correct answers are shown in bold. 1. A longterm radon test a. Is most commonly used for real estate transactions b. Is useful to provide a snapshot of radon activity at a brief moment c. Gives information about a home’s yearround average radon levels d. Lasts 47 days
5. One of the following features does not apply to an activated charcoal adsorption device: a. It is easy to install. b. It is simple to use. c. It is expensive. d. It measures radon over short time periods.
2. Timeintegrated sampling a. Provides the average concentration over a period of time b. Provides the median radon level over a period of time c. Provides a snapshot radon level for a moment in time d. Correlates the radon level in outside air in relation with the indoor level
6. A charcoal liquid scintillation device has the following disadvantage: a. It must be analyzed very quickly after the measurement period ends. b. It requires significant training to use. c. It must be corrected for background gamma radiation. d. It cannot measure for short time periods unless radon concentrations are high.
3. A passive device a. Requires batteries or electricity to operate b. Does not require power to operate c. Does not react to radon or its decay products d. Submits to authority without question 4. One of the following is not a passive radon device: a. Activated charcoal adsorption b. Charcoal liquid scintillation c. Electret ion chamber d. Continuous working level monitor
7. An electret ion chamber measures a. Voltage changes resulting from ions created by radon decay b. The number of ion tracks on a piece of film or plastic c. The adsorption of radon onto an electrically charged disk d. The adsorption of radon into charcoal ions 8. An EPERM device a. Operates well in high humidity b. Is accurate under all temperature conditions
Lesson 518
Measuring radon in residential properties
c. Requires significant training to use d. Requires external power 9. An alpha track detector a. Is expensive b. Is difficult to use c. Does not provide true time integrated measurements d. Is not biased toward most recent exposure
What devices do we use to measure radon?
10. Active devices a. Record measurements once a day b. Work on solar power c. Can show changes in radon levels during the test period d. Are easy to mail
Lesson 519
Measuring radon in residential properties
Handout 53:
What devices do we use to measure radon?
Lesson summary
• Length of test – Shortterm (290 days): provides quick answers but does not provide information about variations from day to day or season to season – Longterm (91365 days): provides more information about yearround radon levels but takes longer to get results • Sampling methods – Timeintegrated sampling: average over a period of time – Continuous sampling: automatic sampling over set intervals of time – Grab sampling: snapshot at a moment in time • Types of devices – Passive (do not require power to operate) • Activated charcoal adsorption • Charcoal liquid scintillation • Electret ion chamber (electrostatic radon monitor) • Alpha track detector – Active (require power to operate) • Continuous radon monitors • Continuous working level monitors
Lesson 520
