lesson 4 what are the units for measuring radon?
TRANSCRIPT
Lesson 4
What are the units for measuring
radon?
Slide 4-2
Radioactivity unitsPicocuries (pCi)
Measures • Activity (radioactive decays/second)• 1 picocurie (pCi)
= 0.037 decays/second = 1 decay/27 seconds= 2.22 decays/minute
Slide 4-3
Radon unitsPicocuries/liter (pCi/L)
Measures • Activity (decays/minute) per volume (one
liter of air)• 1 pCi/L
= 2.22 decays per minute per liter of air
What is the EPA action level in terms of decays per minute per liter of air?
Slide 4-4
EPA action levelPicocuries/liter
4 pCi/L = 4 x 2.22 decays/minute/liter= 8.88 decays/minute/liter
QuestionAssume that a client spent 10 hours/day in a room with a radon level of 4 pCi/L.
How many decays/liter would the client be exposed to each day?
Answer5,328 decays/day/liter
Slide 4-5
International System (SI)Radioactivity units
1 becquerel (Bq)= 1 decay/second= 27 pCi
1 pCi = 0.037 decays/second
= 0.037 Bq
Henri Becquerel, discovered radioactivity in 1896
Slide 4-6
International System (SI)Radon units
1 pCi/L = 37 Bq/m3
Slide 4-7
EPA action level International System (SI)
4 pCi/L = 4 x 37 Bq/m3
= 148 Bq/m3
Slide 4-8
Measuring radon decay products (RDPs)
Measure alpha radiation emitted by short-lived RDPs
Polonium-218
Bismuth-214
Polonium-214
Lead-214
Slide 4-9
Measuring RDPsWorking level (WL)
1 WL = Concentration of RDPs produced from
one liter of air that contains 100 pCi/L of radon
= Amount of short-lived RDPs that exists at a single moment if a container is kept at a constant 100 pCi/L
Slide 4-10
Working levelEPA action level
4 pCi/L = 0.02 WL
Slide 4-11
EPA action level Summary
• 4 pCi/L• 148 Bq/m3
• 0.02 WL
Slide 4-12
Questions?
Slide 4-13
Characteristics of radon decay products (RDPs)
• Solid particles• Electrically charged• React chemically
Slide 4-14
Factors that affect radon and RDP concentrations
• Some radon gas and RDPs escape as air flows out of home
• Some RDPs attach to (plate out on) solid objects, such as– Walls– Floors– Ceilings– Furniture
Plating out• Lowers RDP
concentration in air• Plated out RDPs
cannot be measured• Only RDPs in air can
be measured• Factors that affect
plating out also affect measurement of RDPs
Slide 4-15
Factors that affect radon and RDP concentrations
• Air circulation – Air moving within a
room• Ventilation
– Fresh air entering a room
• Air filters• Particles
suspended in the air – Dust– Smoke– Aerosols
Some RDPs plated out
Slide 4-16
Air circulation
• Circulation = moving around air already in a room
• How would air circulation affect concentration of RDPs?
• May increase plating out, as RDP particles blow toward solid objects and attach to them
• As plating out increases, concentration of RDPs in the air decreases
Fans increase normal air circulation
Slide 4-17
Ventilation
• Ventilation = supply of fresh air
• How would ventilation affect concentration of RFDs?
• Ventilation likely to lower concentration of RFDs• May also reduce radon concentration, as gas
escapes from home
Open windows and doors increase
ventilation
Slide 4-18
Air filter
• How would air filters affect concentration of RFDs?
• Air filters may remove some RDPs, which– Are particles– Have electrical
charge– React chemically
ExampleFurnace air filter
• Air filters will not remove radon, which– Is a gas– Has no electrical
charge– Does not readily
react chemically
Slide 4-19
Particles suspended in air
• Examples– Dust– Smoke– Aerosols
• How would particles affect concentration of RDPs?
• RDPs are more likely to attach to particles• RDP concentration in air decreases
Slide 4-20
Factors may affect radon measurement
• Air circulation• Ventilation• Air filters• Particles in the air
Slide 4-21
Secular (eventual) equilibrium
Radon
Radon decay products
Radon
• In closed home, concentration of RDPs increases until secular equilibrium is reached– Means RDPs have same
level of radioactivity as radon itself
– Takes 3-4 hours– Measure home after it has
reached secular equilibrium
• At secular equilibrium, 1 WL = 100 pCi/L
Slide 4-22
A home inspector’s lament and pledge
Picocuries and becquerels; secular equilibrium.
Radon decaying has made my brain cells go numb.
But I do understand: breathing radon’s not healthy,
So I’ll master these concepts, though they won’t make me wealthy.
Convert all these measurements? Curse that uranium!
I’m working at levels that hurt my poor cranium.
I’ll learn proper techniques, use the right protocol,
To help prevent cancer: that’s the goal of my role.
Slide 4-23
SummaryEPA action level
4 pCi/L = 148 Bq/m3 = 0.02 WL
4 4 pCi/L = 148 Bq/m3 = 0.02 WL
See handout 4-1
Slide 4-24
SummaryFactors affecting measurement
• Air circulation• Ventilation• Air filters• Particles in the air
ImportanceFactors affect conditions for testing a
home
Slide 4-25
Questions?
Slide 4-26
Checkyour comprehension
• See handout 4-2
Slide 4-27
Checkyour understanding
• See handout 4-