RMS System Design & Installation 2 — Questions and Answers
Question 1: When installing a sub-slab depressurization (SSD) system, what is the minimum recommended suction pit diameter?
- 1 inch
- 3 inches (Correct answer)
- 6 inches
- 12 inches
Correct answer: 3 inches
A suction pit of at least 3 inches in diameter is recommended to ensure adequate airflow communication beneath the slab.
Question 2: Which diagnostic test is used to assess how well air moves through the sub-slab material before system design?
- Radon flux test
- Sub-slab communication test (Correct answer)
- Blower door test
- Charcoal canister test
Correct answer: Sub-slab communication test
A sub-slab communication test (using a vacuum or airflow device) determines how freely air moves through the material under the slab, guiding suction point placement.
Question 3: A radon mitigation system installed in a house with a crawl space typically uses which primary method?
- Sub-slab depressurization
- Sub-membrane depressurization (Correct answer)
- Block wall depressurization
- Heat recovery ventilation
Correct answer: Sub-membrane depressurization
Sub-membrane depressurization (SMD) is used in crawl spaces, where a plastic barrier is laid over the soil and a fan draws radon from beneath it.
Question 4: What is the purpose of a U-tube manometer in a radon mitigation system?
- To measure radon gas concentration
- To indicate fan operating pressure differential (Correct answer)
- To monitor crawl space humidity
- To balance air pressure across zones
Correct answer: To indicate fan operating pressure differential
A U-tube manometer installed in the pipe indicates the pressure differential, confirming the fan is operating and creating suction.
Question 5: When routing radon vent pipe through conditioned space, what is required to prevent radon from entering the house if the pipe is breached?
- Double-walled pipe
- Continuous negative pressure maintained throughout the run (Correct answer)
- Rigid PVC only (no flexible pipe)
- Pipe insulation wrapping
Correct answer: Continuous negative pressure maintained throughout the run
EPA standards require that all pipe joints in conditioned space be sealed and that the system maintain negative pressure to prevent radon from leaking into living areas.
Question 6: In a multi-zone SSD system, what component allows the contractor to balance airflow between suction points?
- Backflow preventer
- Adjustable gate valve or damper (Correct answer)
- Pressure relief valve
- Inline HEPA filter
Correct answer: Adjustable gate valve or damper
Adjustable gate valves or dampers allow the contractor to restrict or balance airflow at individual suction points within a multi-zone system.
Question 7: Which slab type presents the greatest challenge for sub-slab depressurization due to limited suction field extension?
- Post-tensioned slab
- Floating slab
- Monolithic slab with gravel sub-base
- Slab-on-grade with fill soil (Correct answer)
Correct answer: Slab-on-grade with fill soil
Slabs poured directly over compacted fill soil with no gravel layer have very limited air movement, making it difficult to extend the suction field from a single point.
RMS System Design & Installation 2
When installing a sub-slab depressurization (SSD) system, what is the minimum recommended suction pit diameter?