RMS Mitigation System Design & Installation 3 — Questions and Answers
Question 1: What does 'extension of radon suction field' mean in the context of SSD system performance?
- Adding more fans to increase total airflow
- The area under the slab influenced by negative pressure from one suction point (Correct answer)
- Extending the exhaust pipe above the roofline
- Increasing the diameter of the suction pipe
Correct answer: The area under the slab influenced by negative pressure from one suction point
The suction field extension describes how far the negative pressure zone spreads beneath the slab from a single suction pit location.
Question 2: A contractor is installing an SSD system in a home with a sump pump pit. What should be done with the sump pit?
- Use the sump pit as the suction point without modification
- Seal the sump pit cover gas-tight and use it as a suction point or install a separate suction pit (Correct answer)
- Remove the sump pump and fill the pit with gravel
- Install the suction point as far as possible from the sump pit
Correct answer: Seal the sump pit cover gas-tight and use it as a suction point or install a separate suction pit
A sump pit can serve as a suction point if sealed with a gas-tight cover, since it already provides access to the sub-slab area.
Question 3: Which of the following is a key difference between active and passive sub-slab depressurization systems?
- Passive systems use a fan; active systems rely on natural stack effect
- Active systems use a fan; passive systems rely on natural stack effect and thermal buoyancy (Correct answer)
- Active systems vent to the attic; passive systems vent through the wall
- Passive systems require larger diameter piping than active systems
Correct answer: Active systems use a fan; passive systems rely on natural stack effect and thermal buoyancy
Active SSD uses a mechanically driven fan, while passive SSD relies solely on natural pressure differences like thermal stack effect without a fan.
Question 4: When performing a building pressure field extension test, a contractor drills a small hole and uses a device to measure air movement. What instrument is used?
- Continuous radon monitor
- Digital manometer or incense stick (Correct answer)
- Carbon monoxide detector
- Combustible gas sniffer
Correct answer: Digital manometer or incense stick
A digital manometer or incense stick/smoke puffer is used to detect air movement and measure pressure differential at the test hole.
Question 5: What minimum vertical height above the roofline must a radon mitigation exhaust pipe terminate according to EPA guidelines?
- 6 inches
- 12 inches (Correct answer)
- 24 inches
- 36 inches
Correct answer: 12 inches
EPA guidelines specify the exhaust pipe must terminate at least 12 inches above the roofline to ensure adequate dispersion of radon.
Question 6: In a house with a crawl space, sub-membrane depressurization (SMD) requires what primary installation step?
- Pouring a concrete slab over the existing soil
- Covering the soil with a gas-tight barrier (polyethylene sheeting) sealed at edges and penetrations (Correct answer)
- Installing a drain tile system beneath the crawl space
- Applying spray foam insulation to all crawl space walls
Correct answer: Covering the soil with a gas-tight barrier (polyethylene sheeting) sealed at edges and penetrations
SMD requires installing a continuous, gas-tight ground cover membrane over crawl space soil, with all edges and penetrations sealed to allow depressurization beneath it.
Question 7: Which factor most significantly reduces the effectiveness of a sub-slab depressurization system?
- Using schedule 40 PVC instead of schedule 80
- Large gaps and cracks in the slab that allow communication between sub-slab and indoor air (Correct answer)
- Installing the exhaust pipe on the north side of the building
- Using a fan with variable speed capability
Correct answer: Large gaps and cracks in the slab that allow communication between sub-slab and indoor air
Unsealed slab cracks and openings allow indoor air to be drawn into the suction field, reducing depressurization effectiveness and increasing operating costs.
RMS Mitigation System Design & Installation 3
What does 'extension of radon suction field' mean in the context of SSD system performance?