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Certified Radon Mitigation Specialist
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A Instant Download Pdf
___________________________________________________________________
1. What is radon?
A. A combustible hydrocarbon gas
B. A naturally occurring radioactive noble gas
C. A manufactured refrigerant
D. A toxic industrial solvent
Answer: A naturally occurring radioactive noble gas
Rationale: Radon is a naturally occurring radioactive gas produced primarily by
the decay of uranium and radium in soil and rock.
2. What is the primary health concern associated with long-term exposure to
radon?
A. Liver failure
B. Skin cancer
C. Lung cancer
D. Kidney disease
Answer: Lung cancer
,Rationale: Radon and its radioactive decay products can damage lung tissue and
are a major cause of lung cancer, particularly among smokers.
3. Which radioactive element is the primary parent of radon-222?
A. Uranium-238
B. Carbon-14
C. Potassium-40
D. Iodine-131
Answer: Uranium-238
Rationale: Radon-222 is produced through the uranium-238 decay series, with
radium-226 serving as its immediate parent.
4. What is the most common isotope of radon encountered in homes?
A. Radon-219
B. Radon-220
C. Radon-222
D. Radon-224
Answer: Radon-222
Rationale: Radon-222 is the principal radon isotope associated with residential
exposure and has a half-life of approximately 3.8 days.
5. What is the EPA action level commonly used for indoor radon?
A. 0.4 pCi/L
B. 1.0 pCi/L
C. 4.0 pCi/L
D. 40 pCi/L
Answer: 4.0 pCi/L
,Rationale: EPA recommends taking action to reduce radon when the indoor
concentration is at or above 4 pCi/L, while also considering reductions below
that level.
6. What does pCi/L stand for?
A. Parts chemical index per liter
B. Picocuries per liter
C. Pressure cubic inches per liter
D. Picograms per cubic liter
Answer: Picocuries per liter
Rationale: pCi/L is a unit used to express radioactive activity concentration in
air.
7. Which pathway commonly allows soil gas containing radon to enter a
building?
A. Sealed windows only
B. Foundation cracks and openings
C. Roof shingles only
D. Interior light fixtures
Answer: Foundation cracks and openings
Rationale: Radon-bearing soil gas can enter through cracks, construction joints,
sump openings, utility penetrations, drains, and other openings in foundations.
8. Why can negative pressure inside a building increase radon entry?
A. It pushes radon into the soil
B. It draws soil gas into the building
C. It destroys radon atoms
D. It increases atmospheric oxygen
Answer: It draws soil gas into the building
, Rationale: Pressure differences between the building and surrounding soil can
create a driving force that pulls radon-containing soil gas indoors.
9. Which building area is often particularly important when evaluating radon
entry?
A. Attic insulation
B. Lowest occupied level in contact with soil
C. Upper roof surface
D. Exterior siding
Answer: Lowest occupied level in contact with soil
Rationale: The lowest level in contact with the ground is often the primary area
to evaluate because it can have direct pathways for soil-gas entry.
10. What is a radon mitigation system designed primarily to do?
A. Destroy uranium in soil
B. Reduce radon entry and/or remove radon from indoor air
C. Increase indoor humidity
D. Seal every exterior wall
Answer: Reduce radon entry and/or remove radon from indoor air
Rationale: Mitigation systems are engineered to reduce indoor radon
concentrations by controlling soil gas and/or improving removal of
contaminated air.
11. Which mitigation approach is commonly used beneath a concrete slab?
A. Sub-slab depressurization
B. Roof ventilation
C. Window replacement only
D. Attic pressurization
Answer: Sub-slab depressurization
Certified Radon Mitigation Specialist
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A Instant Download Pdf
___________________________________________________________________
1. What is radon?
A. A combustible hydrocarbon gas
B. A naturally occurring radioactive noble gas
C. A manufactured refrigerant
D. A toxic industrial solvent
Answer: A naturally occurring radioactive noble gas
Rationale: Radon is a naturally occurring radioactive gas produced primarily by
the decay of uranium and radium in soil and rock.
2. What is the primary health concern associated with long-term exposure to
radon?
A. Liver failure
B. Skin cancer
C. Lung cancer
D. Kidney disease
Answer: Lung cancer
,Rationale: Radon and its radioactive decay products can damage lung tissue and
are a major cause of lung cancer, particularly among smokers.
3. Which radioactive element is the primary parent of radon-222?
A. Uranium-238
B. Carbon-14
C. Potassium-40
D. Iodine-131
Answer: Uranium-238
Rationale: Radon-222 is produced through the uranium-238 decay series, with
radium-226 serving as its immediate parent.
4. What is the most common isotope of radon encountered in homes?
A. Radon-219
B. Radon-220
C. Radon-222
D. Radon-224
Answer: Radon-222
Rationale: Radon-222 is the principal radon isotope associated with residential
exposure and has a half-life of approximately 3.8 days.
5. What is the EPA action level commonly used for indoor radon?
A. 0.4 pCi/L
B. 1.0 pCi/L
C. 4.0 pCi/L
D. 40 pCi/L
Answer: 4.0 pCi/L
,Rationale: EPA recommends taking action to reduce radon when the indoor
concentration is at or above 4 pCi/L, while also considering reductions below
that level.
6. What does pCi/L stand for?
A. Parts chemical index per liter
B. Picocuries per liter
C. Pressure cubic inches per liter
D. Picograms per cubic liter
Answer: Picocuries per liter
Rationale: pCi/L is a unit used to express radioactive activity concentration in
air.
7. Which pathway commonly allows soil gas containing radon to enter a
building?
A. Sealed windows only
B. Foundation cracks and openings
C. Roof shingles only
D. Interior light fixtures
Answer: Foundation cracks and openings
Rationale: Radon-bearing soil gas can enter through cracks, construction joints,
sump openings, utility penetrations, drains, and other openings in foundations.
8. Why can negative pressure inside a building increase radon entry?
A. It pushes radon into the soil
B. It draws soil gas into the building
C. It destroys radon atoms
D. It increases atmospheric oxygen
Answer: It draws soil gas into the building
, Rationale: Pressure differences between the building and surrounding soil can
create a driving force that pulls radon-containing soil gas indoors.
9. Which building area is often particularly important when evaluating radon
entry?
A. Attic insulation
B. Lowest occupied level in contact with soil
C. Upper roof surface
D. Exterior siding
Answer: Lowest occupied level in contact with soil
Rationale: The lowest level in contact with the ground is often the primary area
to evaluate because it can have direct pathways for soil-gas entry.
10. What is a radon mitigation system designed primarily to do?
A. Destroy uranium in soil
B. Reduce radon entry and/or remove radon from indoor air
C. Increase indoor humidity
D. Seal every exterior wall
Answer: Reduce radon entry and/or remove radon from indoor air
Rationale: Mitigation systems are engineered to reduce indoor radon
concentrations by controlling soil gas and/or improving removal of
contaminated air.
11. Which mitigation approach is commonly used beneath a concrete slab?
A. Sub-slab depressurization
B. Roof ventilation
C. Window replacement only
D. Attic pressurization
Answer: Sub-slab depressurization
