RMS Building Science & Radon Entry

Question 1

What is the primary pathway through which radon enters most U.S. residential buildings?

Accepted Answer

Through cracks and openings in the foundation and slab

Answer

Radon, a soil gas, enters buildings primarily through cracks in foundation walls, floor-wall joints, sump pits, and other openings in the lowest structural level in contact with soil.

Question 2

What is the stack effect and how does it relate to radon entry?

Accepted Answer

Warm air rising creates negative pressure at lower levels, drawing in soil gases

Answer

The stack effect occurs when heated indoor air rises and exits through upper levels, creating negative pressure at lower levels that draws soil gases, including radon, into the building.

Question 3

What is the EPA recommended action level for radon in the United States?

Accepted Answer

4 pCi/L (picocuries per liter)

Answer

The EPA recommends that homeowners take action to reduce radon levels at or above 4 pCi/L, while also noting that reducing levels below 2 pCi/L is difficult to achieve.

Question 4

What role does soil permeability play in radon mitigation system design?

Accepted Answer

Higher permeability allows better sub-slab communication and more effective depressurization

Answer

Soil permeability affects how well suction from a mitigation point extends beneath the slab. Highly permeable soils allow better communication, while tight soils may require multiple suction points.

Question 5

What is a sub-membrane depressurization system?

Accepted Answer

A radon system for crawlspaces using a sealed membrane over soil with suction beneath

Answer

Sub-membrane depressurization seals a polyethylene membrane over exposed crawlspace soil, then applies suction beneath the membrane to capture radon before it enters the living space.

(RMS) Radon Mitigation Specialist Practice Test

(RMS) Radon Mitigation Specialist Practice Test

RMS Building Science & Radon Entry