Measuring Radon in Residential Properties How does radon enter a home? Lesson 3 How does radon enter a home? Note that people may also be exposed to radon in schools, offices, other buildings, and mines, but this course focuses on measuring radon in homes. Connecticut Radon Measurement Training Program 2006

Radon in the home For most Americans, greatest exposure to radon is in 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 Homes throughout Connecticut 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 A source of radon A mechanism to transport radon from the source into the home An opening or pathway into the home

Level of radon in a home Depends on Strength of radon sources: most important factor Distance of the sources from the home Ease of transport into the home Ventilation in the home Environmental factors

Measuring Radon in Residential Properties How does radon enter a home? Where radon comes from Uranium-238 Thorium-234 Protactinium-234 Thorium-230 Do not spend a lot of time on this slide. It merely illustrates where radon comes from. Radium-226 Radon-222 See handout 3-1 Connecticut Radon Measurement Training Program 2006

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

Radon source Soil and rock Measuring Radon in Residential Properties How does radon enter a home? Radon source Soil and rock Uranium is present at about 0.5 to 5 parts per million (ppm) in common rocks and soil Uranium and radium especially common in granites, shales, and limestones Under a home, they can be source of radon Uranium decays into radium Radium decays into radon Image: http://www.silverbearcafe.com/private/uranium2.html Connecticut Radon Measurement Training Program 2006

Overview Radon from soil and rock Measuring Radon in Residential Properties How does radon enter a home? Overview Radon from soil and rock Radon enters soil gas Soil gas moves from ground into air in home Usually enters through foundation Cracks in walls and floors Drains Sump holes Dirt floors Construction joints Spaces around service pipes Image: GSF – National Research Center for Environmental Health, Neuherberg, Germany, http://www.gsf.de/Aktuelles/Presse/radon_2004_en.phtml Connecticut Radon Measurement Training Program 2006

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 Measuring Radon in Residential Properties How does radon enter a home? 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 Shower image:http://neatitems.com/images/ISA_Anti-Lime_Champagne_Shower_Spray.jpg Dishwashing image: http://www.h2ouniversity.org/assets/images/kid_washing_dishes.jpg Connecticut Radon Measurement Training Program 2006

Radon in other water Usually not a problem where homes Use surface water (lakes, streams, rivers, and reservoirs) Radon usually escapes into air before it reaches a home Use groundwater from large public systems Water is aerated (mixed with air) and escapes Longer transit times allow most of remaining radon to decay into harmless products

Radon source Building materials Materials sometimes contain radium or uranium Brick Granite Concrete products Sheet rock Materials contaminated with radioactive refuse (rarely used) Usually contribute little to indoor radon

Strength of radon sources Even homes next to each other may have different radon sources, with different strengths. Soil: moderate to weak radon source Groundwater containing radon Rock: moderate radon source Rock: strong radon source Rock: strong radon source

Questions? About radon sources Next Mechanisms that transport radon into a home

Radon transport mechanisms Push or pull radon into a home Air pressure differences Diffusion Emanation Outgassing

Main radon transport mechanism Air pressure differences Measuring Radon in Residential Properties How does radon enter a home? Main radon transport mechanism Air pressure differences Home creates 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 Graphic: U.S. Environmental Protection Agency, 2004, Consumer’s Guide to Radon Reduction: How to Fix Your Home. Connecticut Radon Measurement Training Program 2006

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 Thermal bypasses increase effect Positive pressure  Warm air  Negative pressure    Soil gas  (including radon)

Air pressure differences Mechanical systems Heating, ventilation, and air conditioning (HVAC) systems Air distribution blowers Furnaces Boilers Wood-burning fireplaces Woodstoves Other combustion systems Home exhaust systems (vent air to outside) Clothes dryers Exhaust fans in bathrooms, kitchens, or attics Central vacuum cleaners

Air pressure differences Environmental effects Weather Seasons Rain, snow, and frost Wind Other factors that seal the soil around a home

Environmental effects Seasons Usually more radon enters in winter Warm weather Open windows Equal pressure indoors and outdoors L ess radon enters Good ventilation dilutes radon concentration Cold weather Closed windows Lower pressure indoors More radon enters Poor ventilation traps radon inside

Complex effects of good ventilation (open windows) Reduces vacuum effect Generally reduces radon entry Dilutes radon in home But may also increase stack effect Thereby increases radon entry When you measure radon in short-term tests, should windows be open or closed?

Complex effects of good ventilation (open windows) Reduces vacuum effect Generally reduces radon entry Dilutes radon in home But may also increase stack effect Thereby increases radon entry When you measure radon in short-term tests, windows must be kept closed

Environmental effects Rain, snow, and frost Rain, snow, and frost can seal the soil Prevent radon from escaping from around the foundation Rain can force soil gas into the home

Environmental effects Wind Don’t measure radon during high winds because results may not show typical levels. Wind Higher pressure upwind Lower pressure down-wind Downwind draft effect Changes pressure around the home Higher pressure in soil as wind pushes beneath soil

Environmental effects Factors that seal the soil Prevent radon from escaping into outdoor air Asphalt or concrete driveways Concrete patios

Summary Air pressure Main mechanism that brings radon into a home Difference in air pressure between indoor and outdoor air Main causes of air pressure differences Temperature differences between indoor and outdoor air Mechanical systems Environmental factors

Other radon transport mechanisms Diffusion = movement through materials 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 

Other radon transport mechanisms Emanation = emission of gas from a surface by radioactive decay Some rocks and other building materials contain uranium or radium As these elements decay, radon may be created on their surfaces The radon may be emitted into a room Emanation rate depends on Amount of radioactive materials Surface area of the materials Radon ↑ Radium Uranium Radon

Other radon transport mechanisms Outgassing = release of radon gas from water

Questions? About mechanisms that transport radon into a home Next Pathways that allow radon to enter a home

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

Pathway characteristics Ease with which air moves through the pathway Distance from radium (radon source) Connections with other pathways

Review Requirements for radon entry Radon source Mechanism to transport radon from source into home Pathways into the home These factors determine the amount of radon that enters a home.

Radon levels vary In space From geographic area to geographic area From home to home From level to level within a home Usually highest in lower levels of home Higher readings in upper levels suggest unusual radon entry factors

Radon levels vary Over time In time From season to season From day to day From hour to hour With changes to the home (such as additions) Factors Air pressure changes Wind speed and direction Indoor and outdoor temperature changes Rain, snow, and frost Use of mechanical exhaust systems Because radon levels vary, testing must be done over a period of time

Why this information matters Procedures for measuring radon are designed to control for these factors Air pressure differences Ventilation Environmental effects

Summary Every home should be tested for radon Requirements for radon to enter a home Radon source Mechanism to transport radon Pathway See handout 3-3

Summary Sources Mechanisms Pathways Variation in radon levels Soil and rock Groundwater Building materials Mechanisms Air pressure differences Diffusion Emanation Outgassing Pathways Distance from radon source Ease with which air moves Connections with other pathways Variation in radon levels In space In time With changes in the home

Summary How radon enters a home Measuring Radon in Residential Properties How does radon enter a home? Summary How radon enters a home Source: Natural Resources Canada, http://gsc.nrcan.gc.ca/gamma/radon_e.php Connecticut Radon Measurement Training Program 2006

Activity For a hypothetical client, summarize how radon enters a home Importance of testing every home Factors that determine the radon level in a home Most common sources of radon Common mechanisms of radon entry Pathways into the home Variations in radon levels over space and time Hypothetical client: an attorney

Activity review Is the explanation complete? Is the explanation clear? Does the explanation contain the right level of technical detail for this client? See handout 3-2 for a sample explanation

Questions About how radon enters a home

Check your understanding See handout 3-4