RMS Ventilation & Airflow Management 2 — Questions and Answers
Question 1: What is the primary purpose of a sub-slab depressurization (SSD) system in radon mitigation?
- Increase indoor humidity levels
- Create negative pressure beneath the slab to prevent radon entry (Correct answer)
- Circulate fresh air throughout the building
- Filter radon particles from indoor air
Correct answer: Create negative pressure beneath the slab to prevent radon entry
SSD systems create negative pressure under the foundation slab, preventing radon-laden soil gas from entering the building.
Question 2: When installing a radon mitigation fan in an attic, which factor is most critical for maintaining system effectiveness?
- Fan color to reflect sunlight
- Weatherproof housing rated for temperature extremes (Correct answer)
- Fan motor speed controller
- Decorative housing to match roof aesthetics
Correct answer: Weatherproof housing rated for temperature extremes
Attic-mounted fans must have weatherproof housings rated for the temperature extremes experienced in unconditioned attic spaces.
Question 3: A building has both a basement and a crawl space. What mitigation approach typically provides the most comprehensive radon reduction?
- Treat only the basement since it has greater volume
- Install separate mitigation systems for each area (Correct answer)
- Seal all crawl space vents and install HRV only
- Apply only surface coatings to the basement floor
Correct answer: Install separate mitigation systems for each area
Buildings with multiple sub-structure areas often require separate mitigation systems for each zone to effectively address all radon entry points.
Question 4: Which diagnostic test helps determine if suction points in a sub-slab system are adequately interconnected?
- Radon grab sample
- Communication test using a vacuum cleaner and smoke pencil (Correct answer)
- Blower door test
- Carbon monoxide measurement
Correct answer: Communication test using a vacuum cleaner and smoke pencil
A communication test using a vacuum and smoke pencil verifies that negative pressure from a suction point extends throughout the sub-slab aggregate.
Question 5: What does a manometer reading of -5 Pa at the diagnostic hole indicate in an active SSD system?
- The system is creating positive pressure under the slab
- The fan is drawing negative pressure successfully under the slab (Correct answer)
- The fan has failed and needs replacement
- Radon levels are at 5 pCi/L
Correct answer: The fan is drawing negative pressure successfully under the slab
A negative Pa reading (below zero) confirms the SSD fan is successfully creating the intended negative pressure field beneath the slab.
Question 6: In a block wall foundation, radon mitigation is complicated because:
- Block walls absorb radon and release it slowly
- The hollow cores create multiple pathways for radon to travel (Correct answer)
- Block walls cannot support SSD system pipes
- Radon cannot enter through block walls at all
Correct answer: The hollow cores create multiple pathways for radon to travel
Hollow concrete block cores create interconnected channels throughout the wall that allow radon to migrate and make pressure field extension more complex.
Question 7: Why is it important to discharge radon mitigation system exhaust at least 10 feet above ground or above the roofline?
- To comply with electrical code requirements
- To prevent re-entry of exhausted radon gas into the building (Correct answer)
- To maximize fan efficiency at higher altitudes
- To meet noise ordinance requirements
Correct answer: To prevent re-entry of exhausted radon gas into the building
Discharging exhaust above the roofline or well above ground prevents radon-laden exhaust air from re-entering the building through windows, doors, or air intakes.
RMS Ventilation & Airflow Management 2
What is the primary purpose of a sub-slab depressurization (SSD) system in radon mitigation?