Lesson 5 What devices do we use to measure radon?

Slide 5-1 How long will the test last? Short-term test 2 to 90 days Long-term test 90 to 365 days 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 Disadvantage –Takes longer to get results –Residents forget test is running

Slide 5-2 Sampling methods for radon and radon decay products Time-integrated sampling –Average over a period of time Grab sampling –Snapshot at a moment in time Continuous sampling –Automatic sampling over set intervals of time

Slide 5-3 Standards for devices All devices must meet the requirements of the U.S. Environmental Protection Agency and the National Radon Safety Board Read and follow the directions of the manufacturer of the device you use

Slide 5-4 Types of devices 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

Slide 5-5 Passive devices Activated charcoal adsorption Charcoal liquid scintillation Electret ion chamber (electrostatic radon monitor) Alpha track detector

Slide 5-6 Passive devices Activated 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)

Slide 5-7 Passive devices Activated charcoal adsorption Advantages Requires no external power Inexpensive Easy to place Simple to use Easy to mail to lab Measures over short time periods Gives precise and accurate measurements 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

Slide 5-8 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

Slide 5-9 Passive devices: Charcoal liquid scintillation 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

Slide 5-10 Passive devices Electret ion chamber Most common: electret-passive environmental radon monitor (E-PERM) Use for short-term and long-term tests

Slide 5-11 Passive devices Electret 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

Slide 5-12 Passive devices Electret ion chamber Advantages Requires no external power Provides true integrated measurements Each electret may be reused many times Can provide immediate results Disadvantages 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

Slide 5-13 Use for short-term and long-term tests 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 Passive devices Alpha track detector

Slide 5-14 Passive devices Alpha track detector Advantages Requires no external power Inexpensive Simple to use Easy to mail Provides true integrated measurements –Not biased toward most recent exposure –Can measure over long periods ( days) Disadvantages 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

Slide 5-15 Questions?

Slide 5-16 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 Include (either as an integrated unit or as separate, portable components) –Sampling device –Detector –Analysis system

Slide 5-17 Active devices Continuous radon monitor Continuous working level monitor Use for short-term tests Air either diffuses or is pumped into a counting chamber

Slide 5-18 Active devices Continuous radon monitors Advantages Provide results on-site Give precise, accurate results 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 training to operate Some are sensitive to humidity Some are heavy and bulky

Slide 5-19 Questions?

Slide 5-20 Summary Length of test –Short-term –Long-term Sampling methods –Time-integrated sampling –Grab sampling –Continuous sampling

Slide 5-21 Summary Types of devices –Passive Activated charcoal adsorption Charcoal liquid scintillation Electret ion chamber (electrostatic radon monitor) Alpha track detector –Active Continuous radon monitors Continuous working level monitors