Table of Contents
PPT Slide
Learning Objectives
Radon Entry
Negative Pressures in Building Normally Cause Radon Entry
The Level of Radon in a Building Depends Upon:
Radon Sources
Factors Influencing Radon Source Potential
Mechanism: Direct Entry of Soil Gas-Convective Air Flow
Mechanism: Diffusion-Movement of Radon Through Materials
Mechanism: Emanation-Release of Radon from Surface of Materials
Mechanism: Outgassing from Well Water Supply
Radon Transport via Water Supply
Averaged Contributions from Radon Sources in U.S. Homes
Radon Surveys and Mapping of Potential Areas of Concern
1993: Radon Zone Map By County
Radon Entry Varies from Building to Building
Radon Concentration in Soil Gas Vary from Location to Location
Driving Forces That Cause Radon Entry
Radon Transport Through Soil to Building Requires:
The Predominant Driving Force Is Building Induced Soil Suction
Temperature Induced Pressure Differentials: Stack Effect
Thermal By-Passes Enhance Stack Effect
Radon Levels Are Typically Higher in Lower Levels of Home
Environmental Effects
Environmental Effects: Frost or Other Factors that “Cap” Soil
Rain Effects
Effect of Open Windows
Wind Can Cause Several Effects
Effects of Building Ventilation
Effect of Ventilation Rates on Radon Concentrations
Spot Exhausts in Large Buildings
Unit Ventilators Can Introduce Fresh Air
PPT Slide
Radon Readings in Schools Vary from Room to Room
Room to Room Readings in Large Buildings Are Variable
Mechanical Ventilation Can Affect Radon Entry and Concentrations
Radon Entry Is Variable Since the Driving Forces Are Variable
Pathways And Building Entry Points
There are many pathways for radon to follow to reach a building:
Radon Can Move by Diffusion Through “Tight” Soils
Foundation Type: Pier Building on “Stilts”
Foundation Type: Crawl Space Built Over Enclosed Earthen Area
Foundation Type: Slab-on-Grade Foundation Walls
Foundation Types: Slab-on-Grade Monolithic Pours
Foundation Type: Basement Poured and Block Walls
Floor-to-Wall Joints Can Be Major Entry Points for Slabs
PPT Slide
Man Made Pathways
Slab Penetrations
Plumbing Block-Outs
Radon Entry Through Water Drainage Systems
Unit Summary: Radon Entry and Indoor Concentrations Are Variable
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