RMS Mitigation System Design & Installation 2 — Questions and Answers
Question 1: When installing a sub-slab depressurization (SSD) system in a house with multiple isolated sub-slab areas, what is the recommended approach?
- Install one suction point in the largest section only
- Install separate suction points for each isolated section (Correct answer)
- Increase fan capacity to compensate for isolated sections
- Seal all but one section and install a single suction point
Correct answer: Install separate suction points for each isolated section
Each isolated sub-slab area requires its own suction point because air cannot flow between disconnected sections.
Question 2: Which pipe diameter is most commonly specified for radon mitigation suction pipes in residential installations?
- 2-inch PVC
- 3-inch PVC
- 4-inch PVC (Correct answer)
- 6-inch PVC
Correct answer: 4-inch PVC
4-inch PVC pipe is the most commonly used diameter for residential radon mitigation suction pipes per EPA guidelines.
Question 3: A diagnostic test shows very high sub-slab air resistance (low communication). Which mitigation technique is MOST appropriate?
- Single suction point SSD with a high-capacity fan
- Multiple suction points or sub-membrane depressurization (Correct answer)
- Block wall depressurization only
- Natural ventilation with no mechanical system
Correct answer: Multiple suction points or sub-membrane depressurization
Poor sub-slab communication requires multiple suction points or alternative methods like sub-membrane depressurization to achieve adequate depressurization.
Question 4: What is the purpose of a U-tube manometer installed as part of a radon mitigation system?
- Measure indoor radon concentration continuously
- Indicate whether the fan is creating negative pressure in the suction pipe (Correct answer)
- Monitor carbon dioxide levels near the fan
- Detect moisture in the sub-slab gravel
Correct answer: Indicate whether the fan is creating negative pressure in the suction pipe
A U-tube manometer (system performance indicator) shows homeowners that the fan is operating and maintaining negative pressure in the pipe.
Question 5: When routing the radon mitigation pipe through conditioned living space, what is required?
- The pipe must be insulated with foam wrap
- The pipe must be painted to match interior walls
- All pipe joints must be gas-tight and the pipe must be clearly labeled (Correct answer)
- The pipe diameter must be reduced to 2 inches
Correct answer: All pipe joints must be gas-tight and the pipe must be clearly labeled
Pipes routed through living space must have gas-tight joints and be labeled 'Radon Reduction System' to prevent accidental disconnection.
Question 6: Which foundation type is BEST suited for sub-slab depressurization without major modifications?
- Slab-on-grade with gravel or permeable fill beneath (Correct answer)
- Crawl space with exposed soil
- Basement with poured concrete walls and no sub-slab material
- Pier-and-beam construction
Correct answer: Slab-on-grade with gravel or permeable fill beneath
Slab-on-grade with permeable sub-slab material (gravel) allows easy air movement, making SSD highly effective with minimal modification.
Question 7: After installing a radon mitigation fan in the attic, the contractor must ensure which critical condition is met?
- The fan exhausts into the attic space for dilution
- The fan is placed near an attic vent for natural dilution
- The fan exhaust is discharged above the roofline to the exterior (Correct answer)
- The fan draws air from the attic and pushes it to the sub-slab
Correct answer: The fan exhaust is discharged above the roofline to the exterior
Fan exhaust must always be discharged to the exterior above the roofline so radon cannot re-enter the building through attic vents or openings.
RMS Mitigation System Design & Installation 2
When installing a sub-slab depressurization (SSD) system in a house with multiple isolated sub-slab areas, what is the recommended approach?