Radon Mitigation Professional Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. Which of the following best describes the primary objective of a radon
mitigation system installed in a residential building?
A. Eliminate all radioactive elements from the soil beneath the building
B. Reduce indoor radon concentrations by preventing soil gas entry and/or
removing radon before it enters occupied spaces
C. Increase ventilation by permanently opening all exterior doors and
windows
D. Seal every crack in the foundation without any active components
Answer: B
A radon mitigation system is designed to reduce indoor radon levels by
controlling soil gas pathways, either by preventing entry or by actively
removing radon before it accumulates indoors.
2. Radon is classified as which type of radioactive substance?
A. A stable non-radioactive mineral
B. A naturally occurring radioactive noble gas
C. A synthetic industrial chemical
D. A bacterial contaminant produced in soil
,Answer: B
Radon is a naturally occurring radioactive noble gas produced from the
decay of uranium and radium found in soil, rock, and groundwater.
3. Which radioactive decay product of radon presents the greatest health
concern because it can attach to airborne particles and be inhaled?
A. Radon gas itself only
B. Radon progeny such as polonium, lead, and bismuth isotopes
C. Oxygen molecules
D. Carbon dioxide molecules
Answer: B
The short-lived decay products of radon can attach to dust particles, enter
the lungs, and deliver alpha radiation that increases lung cancer risk.
4. The most common entry route for radon into a building is:
A. Through electrical wiring insulation
B. From indoor furniture materials only
C. Through cracks, joints, and openings in contact with soil
D. Through roof ventilation systems
Answer: C
Radon commonly enters buildings through openings in foundations,
including cracks, construction joints, sump openings, and utility
penetrations.
5. A radon mitigation professional should perform a post-mitigation test
primarily to:
A. Determine the age of the foundation
B. Verify that the mitigation system reduced radon levels effectively
,C. Measure indoor humidity levels
D. Determine the building’s insulation quality
Answer: B
Post-mitigation testing confirms whether the installed system has
successfully reduced radon concentrations to acceptable levels.
6. Which instrument is commonly used for continuous radon
monitoring?
A. Continuous radon monitor
B. Thermometer
C. Carbon monoxide detector
D. Moisture meter
Answer: A
Continuous radon monitors are designed to measure radon concentration
over time and provide detailed readings for evaluation and verification.
7. The action level commonly used by public health authorities for indoor
radon concentration is:
A. 0.4 pCi/L
B. 1.0 pCi/L
C. 4.0 pCi/L
D. 40 pCi/L
Answer: C
A commonly recognized action level for radon mitigation is 4.0 picocuries
per liter (pCi/L), above which corrective action is recommended.
8. Which foundation type most commonly uses a sub-slab
depressurization mitigation system?
, A. Buildings constructed entirely above water
B. Slab-on-grade foundations
C. Buildings without foundations
D. Wooden decks
Answer: B
Sub-slab depressurization is widely used in slab-on-grade structures
because it removes soil gas from beneath the concrete slab.
9. In an active soil depressurization system, the primary purpose of the
fan is to:
A. Heat the soil beneath the building
B. Create negative pressure beneath the foundation to draw soil gases away
C. Increase indoor air pressure
D. Remove moisture from walls only
Answer: B
The mitigation fan creates suction beneath the foundation, reducing the
movement of radon-containing soil gas into the building.
10. Which component prevents rain and debris from entering a
radon exhaust pipe termination?
A. Electrical disconnect
B. Pipe label
C. Rain cap or approved termination design
D. Pressure gauge
Answer: C
Proper exhaust termination protects the system from weather-related
intrusion while allowing safe discharge of radon outdoors.
11. A radon mitigation fan should generally be installed:
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. Which of the following best describes the primary objective of a radon
mitigation system installed in a residential building?
A. Eliminate all radioactive elements from the soil beneath the building
B. Reduce indoor radon concentrations by preventing soil gas entry and/or
removing radon before it enters occupied spaces
C. Increase ventilation by permanently opening all exterior doors and
windows
D. Seal every crack in the foundation without any active components
Answer: B
A radon mitigation system is designed to reduce indoor radon levels by
controlling soil gas pathways, either by preventing entry or by actively
removing radon before it accumulates indoors.
2. Radon is classified as which type of radioactive substance?
A. A stable non-radioactive mineral
B. A naturally occurring radioactive noble gas
C. A synthetic industrial chemical
D. A bacterial contaminant produced in soil
,Answer: B
Radon is a naturally occurring radioactive noble gas produced from the
decay of uranium and radium found in soil, rock, and groundwater.
3. Which radioactive decay product of radon presents the greatest health
concern because it can attach to airborne particles and be inhaled?
A. Radon gas itself only
B. Radon progeny such as polonium, lead, and bismuth isotopes
C. Oxygen molecules
D. Carbon dioxide molecules
Answer: B
The short-lived decay products of radon can attach to dust particles, enter
the lungs, and deliver alpha radiation that increases lung cancer risk.
4. The most common entry route for radon into a building is:
A. Through electrical wiring insulation
B. From indoor furniture materials only
C. Through cracks, joints, and openings in contact with soil
D. Through roof ventilation systems
Answer: C
Radon commonly enters buildings through openings in foundations,
including cracks, construction joints, sump openings, and utility
penetrations.
5. A radon mitigation professional should perform a post-mitigation test
primarily to:
A. Determine the age of the foundation
B. Verify that the mitigation system reduced radon levels effectively
,C. Measure indoor humidity levels
D. Determine the building’s insulation quality
Answer: B
Post-mitigation testing confirms whether the installed system has
successfully reduced radon concentrations to acceptable levels.
6. Which instrument is commonly used for continuous radon
monitoring?
A. Continuous radon monitor
B. Thermometer
C. Carbon monoxide detector
D. Moisture meter
Answer: A
Continuous radon monitors are designed to measure radon concentration
over time and provide detailed readings for evaluation and verification.
7. The action level commonly used by public health authorities for indoor
radon concentration is:
A. 0.4 pCi/L
B. 1.0 pCi/L
C. 4.0 pCi/L
D. 40 pCi/L
Answer: C
A commonly recognized action level for radon mitigation is 4.0 picocuries
per liter (pCi/L), above which corrective action is recommended.
8. Which foundation type most commonly uses a sub-slab
depressurization mitigation system?
, A. Buildings constructed entirely above water
B. Slab-on-grade foundations
C. Buildings without foundations
D. Wooden decks
Answer: B
Sub-slab depressurization is widely used in slab-on-grade structures
because it removes soil gas from beneath the concrete slab.
9. In an active soil depressurization system, the primary purpose of the
fan is to:
A. Heat the soil beneath the building
B. Create negative pressure beneath the foundation to draw soil gases away
C. Increase indoor air pressure
D. Remove moisture from walls only
Answer: B
The mitigation fan creates suction beneath the foundation, reducing the
movement of radon-containing soil gas into the building.
10. Which component prevents rain and debris from entering a
radon exhaust pipe termination?
A. Electrical disconnect
B. Pipe label
C. Rain cap or approved termination design
D. Pressure gauge
Answer: C
Proper exhaust termination protects the system from weather-related
intrusion while allowing safe discharge of radon outdoors.
11. A radon mitigation fan should generally be installed:
