Radon Mitigation Professional Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. A primary objective of a residential radon mitigation system is to:
A. Eliminate all naturally occurring radioactive materials from the soil
B. Reduce indoor radon concentrations to as low as reasonably
achievable by preventing soil gas entry
C. Increase indoor humidity to dilute radon concentrations
D. Prevent all air exchange between indoors and outdoors
Rationale: The purpose of radon mitigation is to reduce indoor radon levels
by controlling soil gas entry and safely venting radon outdoors. Complete
elimination of radon is generally impossible because it is naturally present
in the environment.
2. Which foundation type generally presents the greatest challenge for
sub-slab depressurization system design?
A. Monolithic slab-on-grade without interior footings
B. Suspended wood floor over an open crawl space
C. Homes with multiple foundation types and interconnected slabs
D. Elevated pier foundation without enclosed crawlspace
,Rationale: Structures with multiple foundation types often require
separate suction points or multiple mitigation strategies because pressure
fields may not communicate effectively between foundation sections.
3. The primary driving force behind soil gas entry into buildings is:
A. Wind pressure alone
B. Capillary action
C. Pressure differences between the building interior and
surrounding soil
D. Solar radiation
Rationale: Negative pressure inside buildings relative to surrounding soil
draws radon-containing soil gas through cracks and openings into occupied
spaces.
4. Before installing a mitigation system, the mitigator should first:
A. Install the fan
B. Seal every visible crack
C. Conduct a thorough diagnostic evaluation of the structure
D. Replace all basement windows
Rationale: A complete building evaluation identifies foundation
characteristics, entry routes, HVAC influences, and optimal system
locations before installation begins.
5. Which instrument is commonly used to evaluate pressure field
extension beneath a slab?
A. Hygrometer
B. Infrared thermometer
C. Micromanometer
D. Light meter
, Rationale: A micromanometer measures very small pressure differences
and is essential for determining whether adequate sub-slab
communication has been established.
6. A mitigation fan should normally be installed:
A. Inside occupied living rooms
B. Inside bedrooms
C. Outside conditioned living spaces whenever possible
D. Inside return-air ducts
Rationale: Locating fans outside occupied areas reduces the risk that leaks
in the fan housing could introduce concentrated radon into living spaces.
7. Which material is commonly used for radon vent piping in residential
systems?
A. Copper tubing
B. PVC pipe
C. Galvanized steel conduit
D. Flexible dryer duct
Rationale: PVC piping is durable, corrosion resistant, readily available, and
commonly specified for residential radon mitigation systems.
8. Why should mitigation system exhaust terminate above the roofline?
A. To improve fan cooling
B. To reduce installation cost
C. To minimize the possibility of radon re-entering the building
D. To protect roofing shingles from sunlight
Rationale: Discharging above the roof promotes atmospheric dilution and
reduces the likelihood that radon will re-enter through windows, doors, or
air intakes.
9. Which crack represents a significant potential radon entry pathway?
A. Surface paint crack
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. A primary objective of a residential radon mitigation system is to:
A. Eliminate all naturally occurring radioactive materials from the soil
B. Reduce indoor radon concentrations to as low as reasonably
achievable by preventing soil gas entry
C. Increase indoor humidity to dilute radon concentrations
D. Prevent all air exchange between indoors and outdoors
Rationale: The purpose of radon mitigation is to reduce indoor radon levels
by controlling soil gas entry and safely venting radon outdoors. Complete
elimination of radon is generally impossible because it is naturally present
in the environment.
2. Which foundation type generally presents the greatest challenge for
sub-slab depressurization system design?
A. Monolithic slab-on-grade without interior footings
B. Suspended wood floor over an open crawl space
C. Homes with multiple foundation types and interconnected slabs
D. Elevated pier foundation without enclosed crawlspace
,Rationale: Structures with multiple foundation types often require
separate suction points or multiple mitigation strategies because pressure
fields may not communicate effectively between foundation sections.
3. The primary driving force behind soil gas entry into buildings is:
A. Wind pressure alone
B. Capillary action
C. Pressure differences between the building interior and
surrounding soil
D. Solar radiation
Rationale: Negative pressure inside buildings relative to surrounding soil
draws radon-containing soil gas through cracks and openings into occupied
spaces.
4. Before installing a mitigation system, the mitigator should first:
A. Install the fan
B. Seal every visible crack
C. Conduct a thorough diagnostic evaluation of the structure
D. Replace all basement windows
Rationale: A complete building evaluation identifies foundation
characteristics, entry routes, HVAC influences, and optimal system
locations before installation begins.
5. Which instrument is commonly used to evaluate pressure field
extension beneath a slab?
A. Hygrometer
B. Infrared thermometer
C. Micromanometer
D. Light meter
, Rationale: A micromanometer measures very small pressure differences
and is essential for determining whether adequate sub-slab
communication has been established.
6. A mitigation fan should normally be installed:
A. Inside occupied living rooms
B. Inside bedrooms
C. Outside conditioned living spaces whenever possible
D. Inside return-air ducts
Rationale: Locating fans outside occupied areas reduces the risk that leaks
in the fan housing could introduce concentrated radon into living spaces.
7. Which material is commonly used for radon vent piping in residential
systems?
A. Copper tubing
B. PVC pipe
C. Galvanized steel conduit
D. Flexible dryer duct
Rationale: PVC piping is durable, corrosion resistant, readily available, and
commonly specified for residential radon mitigation systems.
8. Why should mitigation system exhaust terminate above the roofline?
A. To improve fan cooling
B. To reduce installation cost
C. To minimize the possibility of radon re-entering the building
D. To protect roofing shingles from sunlight
Rationale: Discharging above the roof promotes atmospheric dilution and
reduces the likelihood that radon will re-enter through windows, doors, or
air intakes.
9. Which crack represents a significant potential radon entry pathway?
A. Surface paint crack
