Radon Overview How Radon Enters the Home

Learning Outcomes Upon completion of this module you will be able to:  Recall the predominant source of radon in the home  Identify the three requirements for radon to enter a home  Recognize what household activities release radon in water into the air

Learning Outcomes  Determine why one home has high radon levels but the next door neighbor does not  Identify the main radon transport mechan- ism into a home  Examine why radon levels in a home are higher in the winter than in the summer Upon completion of this module you will be able to:

Radon in the Home  For most Americans, the greatest exposure to radon is in the home, especially in rooms that are:  Below grade (such as basements)  In contact with the ground  Immediately above the first two categories  High radon levels have been found in:  Homes throughout the United States  Every type of home ▪ Old or new ▪ Drafty or well sealed ▪ With or without a basement

Importance of Testing  Even neighboring homes may have very different radon levels  EPA recommends that all homes be tested for radon  Testing is the only accurate way to determine the radon level in any home

Requirements for Radon to Enter a Home 1. A source of radon 2. A mechanism to transport radon from the source into the home 3. An opening or pathway into the home

Sources of Radon  Soil and rock: most common source  Groundwater  Building materials containing uranium and radium

Overview: Radon From Soil and Rock Radon enters soil gas. Soil gas moves from the ground into air in the home, usually through the foundation in:  Drains  Cracks in walls and floors  Sump holes  Dirt floors  Construction joints  Spaces around service pipes

Radon Source: Groundwater Usually a problem only in small, closed water systems:  Where underlying rocks contain high levels of uranium  Where homes rely on groundwater from private wells or small public waterworks as the main water source

Radon from Groundwater Sources  Radon does not have time to decay into harmless by- products before entering a home  Once inside the home, radon escapes from the water into the air during normal household activities:  Showering  Washing clothes or dishes  Flushing toilets

Radon Source: Emanation  Building materials sometimes contain radium or uranium  Brick  Granite  Concrete products  Sheetrock  Materials contaminated with radioactive refuse (rarely used)  Usually contribute little to indoor radon

Strengths of Radon Sources Even homes next to each other may have different radon sources with different strengths. Rock: strong source Groundwater: weak source Soil: moderate source

Radon Transport Mechanisms  Push or pull radon into a home  Air pressure differences  Diffusion  Emanation  Outgassing

Main Radon Transport Mechanism: Air Pressure Differences  Home creates a small vacuum (negative air pressure)  Draws in soil gas, including radon  Vacuum caused by:  Temperature differences between outside and inside air (stack effect)  Mechanical systems  Environmental factors

Air Pressure Differences: Stack Effect  Heated indoor air rises and escapes through cracks and holes at top of home  Creates positive air pressure at top of home  Creates negative air pressure (vacuum) at bottom  Vacuum draws in soil gas, including radon  Effect is greatest during coldest months Positive pressure  Warm air  Negative pressure  Soil gas  (including radon)

Environmental Effects: Seasons Warm Weather  Open windows  Equal pressure indoors and outdoors  Less radon enters  Good ventilation dilutes radon concentration Cold Weather  Closed windows  Lower pressure indoors  More radon enters  Poor ventilation traps radon inside

Another Transport Mechanism: Diffusion  Radon concentration is higher at its source (underlying soil or foundation) than in indoor air  Radon moves from area of higher concentration to area of lower concentration Lower radon concentration  Higher radon  concentration 

Radon Pathways into the Home  Natural pathways  Pores or empty spaces in soil  Cracks in underlying rocks  Earthen areas in basements  Artificial pathways  Openings for utility lines and plumbing  Water drainage systems  Other openings in foundations

Summary In this module we discussed:  The predominant source of radon in the home  The three requirements for radon to enter a home  What household activities release radon in water into the air

Summary  Why one home has high radon levels but the next door neighbor does not  The main radon transport mechanism into a home  Why radon levels in a home are higher in the winter than in the summer In this module we discussed: