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8/6/2019 Radon Measurements Mitigation
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Same number of protons as another atom, but adifferent number of neutrons
Example: Radon 220 is isotope of Radon 222
Both have 86 protons
Radon 220 has 134 neutrons
Radon 222 has 136 neutrons
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K Radiation
E Radiation
Occurs spontaneously
Due to change in # ofprotons, atombecomes -2 charge
Radiation released
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Alpha Radiation (E)
Particle released when the nucleus
kicks out 2 neutrons and 2 protons Relatively massive
Relatively slow
Total charge of +2
Mass number changes by 4 and atomic
number changes by 2
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Beta Radiation (F)
Particle released when the nucleus
changes a neutron into a proton and abeta particle
Relatively small mass
Relatively fast moving
Total charge of -1
Atomic Mass Number remains constant
F
PN
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Gamma Radiation (K)
Pure energy. Released from the
nucleus when an alpha or a beta isemitted
No mass
Speed of light
No charge
NO CHANGE
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E
K
F
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Radon-222 is a radioactive gas released duringthe natural decay of thorium and uranium
Colorless
Odorless
Tasteless
Radon cannot be detected with the human senses
Naturally Occurring in rock and soil
Radioactive
Inert
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Radon decays into
Radon DecayProducts
It is these products that produce the harmfulradiation!
Polonium 214
Polonium 218
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Decay Products of Radon are charged ions
Have a static charge
Easy attachment to
water vapor
dust
smoke particles
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ie. Granite, shale, phosphate,
and pitchblende
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(Solid)
Halflife: 4.47 billion years
(Solid)
Halflife: 1,620 years
(Gas)
Halflife: 3.8 days
Polonium 214 & 210
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E K
F K
F K
F K
F K
F K
F K
E K
E K
E K
E K
E K
E K
E K
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It is the E
emitters from theRDPs that causethe most damage
to lung tissuewhen they are
inhaled.
E K
F K
F K
E K
radon progeny (daughters)radioactive isotopes oflead, bismuth, and poloniumcan be inhaled and deposited in the lungs
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S f R di ti E i U
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Sources of Radiation Exposure in U
Medical X-rays
11%
Radon54%
Cosmic8%
Terrestrial8%
Consumer Products3%
Nuclear Medicine4%
Internal11%
Other1%
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SOURCESOF RADON
Outdoors radon poses significantly less risk than indoors.
Indoors radon can accumulate to significant levels.
The magnitude of radon concentration indoors depends
primarily on a building's construction and the amount of radon
in the underlying soil.
Radon gas can enter a buildings from the soil through cracks
in concrete floors and walls, floor drains, sump pumps,
construction joints, and tiny cracks or pores in hollow-block
walls. Radon levels are generally highest in basements and ground
floor rooms that are in contact with the soil.
Well water is another source of radon.
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HOW RADON ENTERS A BUILDING
A. Cracked slab
B. Spaces between bricks
C. Pores in concrete blocks
D. Floor-wall joints
E. Exposed soil
F. Weeping drain tile
G. Mortar joints
H. Loose fitting pipeI. Open tops of block walls
J. Building materials (rock)
K. Well water
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Air movement through soil
Cracks in foundations
Through well water
Also through some buildingmaterials (ie. Concrete)
that have the potential tocontain and emit Radon.
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When exhaust fansremove air from a
building, much of the
replacement aircomes from the soil
underneath thebuilding.
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When indoor temperaturesare higher than outdoortemperatures and thewarm air rises, it is
replaced with the cooler,more dense air from theoutside. Some of this airmoves through the soil
and carries radon with it.
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Radioactive decayof Radon atom
Emits E radiation Emits K radiation
Radon Decay Products
Polonium 218
Polonium 214
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RDPs stickto the lung
tissue.
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Damage to
lung tissue
Lung TissueCell
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Between 48 hoursand less than 90days duration
Closed houseconditions 12 hrsprior to testing
Commonly usedduring real estatetransactions
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Duration longer than 90days
Closed house conditions12 hrs prior to testing
Provide more accuratereadings
Take into account all
variables: weather
occupancy
heating/cooling
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RADONTESTING
Professional radon testing services can cost as high as $300. Home radon test kits can cost as little as $10 per kit.
Two types of methods to detect radon.
Radon Gas Measurement Methods: Detect the amount of
radon gas build-up.
Radon Decay Measurement Methods. These look at the
source material and measure how much radioactive decay
has taken place.
The most accurate and reliable radon measurements are those
that continuously monitor radon.
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Activated CharcoalAdsorption
Radon is absorbed into a charcoal canisterShort-term detector (equilibration over 2-7 days)
Laboratory analysis by scintillation (gamma-ray)
Alpha Track Detection
A plastic film is exposed (1 to 12 months)
Alpha particles from radon decay produce damage tracksNumber of damage tracks determined
Integrating detector
Continuous Radon Monitoring (Scintillation counter)
Radon decay event causes electric current pulse in device
Real-time detector
Signal can be electronically integrated (pulse counting)
Electret Ion Chamber (Electrostatically charged disk detector)
Radon decay ionizes air
Air conductivity increases, reducing voltage across chamber
Real-time detector
Signal can be electronically integrated
RADON GASMEASUREMENT METHODS
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RADONGAS MEASUREMENT METHODS
1. AC - Activated Charcoal Adsorption
Uses an airtight container with activated charcoalthat is opened in the area to be sampled and radon
in the air adsorbs onto the charcoal granules. At the end of the sampling period, the container issealed and may be sent to a laboratory for analysis.
The gamma decay from the radon adsorbed to thecharcoal is counted
Charcoal adsorption detectors, depending ondesign, are deployed from 2 to 7 days.
Use of a diffusion barrier over the charcoal reducesthe effects of drafts and high humidity.
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RADONGAS MEASUREMENT METHODS
2.Alpha Track Detection (filtered)
The detector is a small piece of special plastic or filminside a small container.
Air being tested diffuses through a filter covering ahole in the container. When alpha particles from radonand its decay products strike the detector, they causedamage tracks. At the end of the test the container issealed and returned to a laboratory for reading.
Exposure of alpha track detectors is usually 3 to 12months, but because they are true integrating devices,alpha track detectors may be exposed for shorterlengths of time when they are measuring higher radonconcentrations.
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RADONGAS MEASUREMENT METHODS
3.Unfiltered Track Detection
The unfiltered alpha track detector operates on the
same principle as the alpha track detector, exceptthat there is no filter present to remove radon decay
products and other alpha particle emitters.
EPA currently recommends that these devices not
be used when the equilibrium fraction is less than
0.35 or greater than 0.60 without adjusting the
calibration factor.
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RADONGAS MEASUREMENT METHODS
4. Charcoal Liquid Scintillation This method employs a small vial containing
activated charcoal for sampling the radon.
After an exposure period of 2 to 7 days (depending
on design) the vial is sealed and returned to a
laboratory for analysis.
Analysis is accomplished by treating the charcoal
with a scintillation fluid, then analyzing the fluid
using a scintillation counter. The radon concentration
of the sample site is determined by converting from
counts per minute.
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RADONGAS MEASUREMENT METHODS
5. Continuous Radon Monitoring
This method category includes those devices that
record real-time continuous measurements of radon gas.
Air is either pumped or diffuses into a counting
chamber. The counting chamber is typically a
scintillation cell or ionization chamber.
Scintillation counts are processed by electronics, and
radon concentrations for predetermined intervals are
stored in the instrument's memory or transmitted
directly to a printer.
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RADONGAS MEASUREMENT METHODS
6. Electret Ion Chamber: Long-Term & Short-Term
For this method, an electrostatically charged diskdetector (electret) is situated within a small container(ion chamber).
During the measurement period, radon diffusesthrough a filter-covered opening in the chamber, wherethe ionization resulting from the decay of radon and itsprogeny reduces the voltage on the electret.
EL detectors may be deployed for 1 to 12 months.Since the electret-ion chambers are true integratingdetectors, the EL type can be exposed at shorterintervals if radon levels are sufficiently high.
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RADONGAS MEASUREMENT METHODS
8. Grab Radon/Activated Charcoal
Requires a skilled technician to sample radon by
using a pump or a fan to draw air through acartridge filled with activated charcoal.
Sampling takes from 15 minutes to 1 hour.
After sampling, the cartridge is placed in a sealed
container and taken to a laboratory where analysis is
approximately the same as for the AC or LS
methods.
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RADONGAS MEASUREMENT METHODS
9. Grab Radon/Pump-Collapsible Bag
10. Grab Radon/Scintillation Cell
11. Three-Day Integrating Evacuated Scintillation Cell
12. Pump-Collapsible Bag (1-day)
13. Continuous Working Level Monitoring
14. Grab Working Level
15. Radon Progeny (Decay Product) Integrating SamplingUnit
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RADON MITIGATIONSTRATEGIES
EPA generally recommends methods which preventthe entry of radon.
Reducing radon entry by:
- Collecting it prior to entry into the building anddischarging it to a safe location.
- Modifying building pressure differentials or sealing
entry points.
Methods that reduce radon concentrations afterentry by:
- Dilution with increased ventilation.
- Filtering radon from the air.
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SUB-SLAB DEPRESSURIZATION
Reduces radonconcentrations 80-99%
Works best if air
can move easilythrough the soil underthe slab.
Costs normally are
under $3000 with anannual heat/airconditioning loss of$150-200.
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SUMP/DRAIN-TILE DEPRESSURIZATION
Reduces radonlevels by 90-99%.
It works best if
drain tiles form acomplete loop aroundthe building.
Costs normally areunder $2000 with anannual heat/airconditioning loss of$150-200.
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BLOCK WALL DEPRESSURIZATION
Reduces radon 50-99%.
Works only in
buildings that havehollow block walls.
Requires sealing ofthe openings.
Costs $3000 withan annual loss of$150-300 for air
conditioning/ heating.
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SUB-SLAB PRESSURIZATION
Works best withtight basementsisolated from outdoorsand upper floors.
Discourages entryof radon.
Reduces radon by
50-99%
Costs $500-1,500.
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VENTILATION
There are various ventilation approaches such as:
Isolating and ventilating substructures such ascrawl spaces.
Passively adding fresh air make-up to workingspaces.
Actively adding fresh air make-up to a workingspace while removing interior air with some means ofheat recovery.
It should be noted that during ventilation methods,there is significant heat and air conditioning air lossresulting in higher utility bills.
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CHARCOAL ADSORPTIONFOR LOW
LEVELSOF RADON
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HEPA FILTRATIONOF RADON
DECAY PRODUCTS
High Efficiency Particulate Air (HEPA) filters
screen the finest particles out.
Many Radon Decay Products (RDPs) plate out on
the surface of the filter.
HEPA filters screen out other air contaminants.
HEPA filters must be placed in many rooms or in
the central air conditioning system. Use of a HEPA filtration system of Radon Decay
Products still requires radon test monitoring.
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ELECTROSTATIC AIR CLEANERS
Electrostatic air cleaners remove dust particles
that have Radon Decay Products attached. These
cleaners do not effect the radon.
As dust particles are removed from the air, theunattached fraction of RDPs can increase in the
room.
These cleaners remove other air contaminants and
like the HEPA filter they must be placed in everyroom or in a central air conditioner.
Electrostatic air cleaners must have a radon
testing device to measure their effectiveness.
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OTHER TECHNIQUESSealing Cracks
Sealing cracks and other openings in the foundation isa basic part of most approaches to radon reduction.
Sealing does two things, it limits the flow of radoninto the building and reduces the loss of conditioned air.
EPA does not recommend the use of sealing alone toreduce radon
Pressurization
Pressurization uses a fan to blow air into the
basement or work area from either upstairs oroutdoors.
It creates enough pressure at the lowest level indoorsto prevent radon from entering into the building.
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OTHER TECHNIQUES
Heat Recovery Ventilator Heat recovery ventilators (HRV), also called an
air-to-air heat exchangers, can be installed to
increase ventilation.
An HRV will increase building ventilation whileusing the heated or cooled air being exhausted to
warm or cool the incoming air.
HRVs also can improve air quality in buildings
that have other indoor pollutants. There could be
significant increase in the heating and cooling costs
with an HRV, but not as great as ventilation without
heat recovery.
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RADONINWATER
Radon is able to dissolve in water.
The radon gas later escapes from the water and
goes into the air, raising the rooms radon content.
Each year, 183 people die from exposure to radon
in drinking water.
The primary health risks from radon in drinkingwater are lung cancer, from inhaling radon
discharged from water used in the home.
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RADONINWATER
There is currently no federally-enforced drinkingwater standard for radon.
EPA is proposing to regulate radon in drinking
water from community water suppliers.
EPA does not regulate private wells.
EPA is proposing to require community water
suppliers to provide water with radon levels no higher
than 4,000 pCi/L, which contributes about 0.4 pCi/Lof radon to the air in your building.
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RADONINWATER
Radon can be removed from water by using one oftwo methods: aeration treatment or granular activatedcarbon (GAC) treatment.
Aeration treatment involves spraying water ormixing it with air, and then venting the air from the
water before use. Aeration is more efficient than GAC. GAC treatment filters water through carbon. Radonattaches to the carbon and leaves the water free ofradon.
Some building owners opt for a service contractfrom the installer to provide for carbon replacementand general system maintenance.
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Radon Measurements taken in the lowest occupied levelof the home.
If the initial measurement is> 4pCi/L then repeat test in
same location. If the second measurementis > 4pCi/L, consult with acertified Radon Mitigator aboutmitigation.
If the initial measurement is< 4pCi/L then use results.
Mitigation is not necessary.
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THE IMPORTANCE OF A CLEAN
ENVIRONMENT
I would ask all of us to remember that protecting our
environment is about protecting where we live and
how we live.
Let us join together to protect our health, our
economy, and our communities -- so all of us and our
children and our grandchildren can enjoy a healthy
and a prosperous life.