Transcript 05Whatdevicesdoweuse7-19

Lesson 5
What devices do we
use to measure
radon?
How long
will the test last?
Short-term test
Long-term test
2 to 90 days
90 to 365 days
Advantage
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
– Provides more
information about yearround average radon
level
Disadvantage
– Takes longer to get
results
– Residents forget test is
running
Slide 5-1
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 5-2
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 5-3
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 5-4
Passive devices
• Activated charcoal adsorption
• Charcoal liquid scintillation
• Electret ion chamber (electrostatic
radon monitor)
• Alpha track detector
Slide 5-5
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 5-6
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 5-7
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 5-8
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 5-9
Passive devices
Electret ion chamber
• Most common:
electret-passive
environmental
radon monitor
(E-PERM)
• Use for short-term
and long-term
tests
Slide 5-10
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 5-11
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
Slide 5-12
of tampering
Passive devices
Alpha track detector
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
Slide 5-13
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 (90-365 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 5-14
Questions?
Slide 5-15
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 5-16
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 5-17
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 5-18
Questions?
Slide 5-19
Summary
• Length of test
– Short-term
– Long-term
• Sampling methods
– Time-integrated sampling
– Grab sampling
– Continuous sampling
Slide 5-20
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
Slide 5-21