Radon "Red Flags"
Radon is a colorless, odorless gas with no immediate health effects. Because of this, it's impossible to deem a property "radon-free" by visual inspection alone. That being said, inspecting a property for certain "red flags" can provide useful information on how radon might enter a building and how radon problems can be fixed. Air testing will still be required to determine how much radon is present before and after protective measures are put in place, but knowing how it's able to enter indoor spaces can make it easier to correct the issue.
The major red flags indicating that a problem might be present are:
1. The property's geographic location,
2. Structural points of entry,
3. The presence of previously installed mitigation systems,
4. The presence of mechanical systems that reduce air pressure in below-grade structures, and/or
5. Use of well water
Geographic Location
Location can provide insight into whether radon is likely to be a problem in a home or non-residential property. Certain areas of the United States are more prone to radon problems due to area geology. Regions with high concentrations of of naturally occurring uranium in their soil and sediments tend to be at highest risk. As these elements undergo radioactive decay, they convert to radon gas, which is able to enter and accumulate in indoor air. This becomes a particular problem when soils are permeable to gas and substances like radon can move relatively freely underground through soil pore space.
In the United States, the EPA designates areas as having high "radon potential" if radon concentrations in soil are high, if indoor readings indicate high radon levels are typical, if geological conditions permit for easy underground migration, and based upon building stocks common to the region. In general, areas along the eastern, southern and western coastlines have low radon potential, and the central northern, midwestern, and the eastern mountain regions have elevated radon potential. You can see the EPA's radon potential maps and read more about how they were created here, on the EPA's website.
Structural Points of Entry
Crumbling and compromised building foundations can act as pathways whereby radon can leave the soil and enter homes. Evidence of cracking or crumbling can be a major red flag, as can other structural modifications typically associated with indoor moisture reduction. Unpaved basements, basement trenches, sumps, and drains are some structures that also allow radon to enter into homes and buildings.
Radon Mitigation Systems
If you notice ducts, pumps, vents and/or fans that aren't associated with building heating and air conditioning systems, they could possibly indicate a past or current radon problem. These items are associated with radon mitigation systems, mechanical systems put in place to reduce indoor radon concentrations. Although their presence might suggest that the problem has been fixed, this is not always the case. Many radon mitigation systems become ineffective over time, and systems that were never installed properly or are in disrepair due to age might not be able to remove radon to the degree that is required to protect human health. If present, radon mitigation systems should be functionally assessed.
Mechanical Systems that Reduce Indoor Air Pressure
Even a small drop in indoor air pressure can draw radon from the soil into one's home. This being the case, mechanical systems that artificially reduce pressure can be a big cause for concern. Two notable mechanical systems that can draw radon into buildings are sump pumps and elevators. Sump pumps can be very effective at bringing radon indoors and can cause major problems. If not properly sealed, their wells can act as a conduit for radon migration while their vacuum draws radon from beneath the basement slab. Likewise, the piston effect that occurs when elevator cars move between floors can act to create suction and distribute radon throughout a building.
Well Water
Although most significant indoor radon exposures come from soil, groundwater can contribute to exposure in some instances as well. Well water that is high in radon can release the toxic gas when used for cooking and showering activities. Unlike municipally water, which is typically treated for several days prior to distribution (a process which allows the naturally present radon to decay), well water usually travels directly from the groundwater source to the tap. As a result, this type of water can be several degrees of concentration greater that expected for municipally treated water. In instances where bathroom ventilation is poor, the radon gas can become trapped within the confines of bathrooms or kitchens leading to high levels of personal exposure.
The major red flags indicating that a problem might be present are:
1. The property's geographic location,
2. Structural points of entry,
3. The presence of previously installed mitigation systems,
4. The presence of mechanical systems that reduce air pressure in below-grade structures, and/or
5. Use of well water
Geographic Location
Location can provide insight into whether radon is likely to be a problem in a home or non-residential property. Certain areas of the United States are more prone to radon problems due to area geology. Regions with high concentrations of of naturally occurring uranium in their soil and sediments tend to be at highest risk. As these elements undergo radioactive decay, they convert to radon gas, which is able to enter and accumulate in indoor air. This becomes a particular problem when soils are permeable to gas and substances like radon can move relatively freely underground through soil pore space.
In the United States, the EPA designates areas as having high "radon potential" if radon concentrations in soil are high, if indoor readings indicate high radon levels are typical, if geological conditions permit for easy underground migration, and based upon building stocks common to the region. In general, areas along the eastern, southern and western coastlines have low radon potential, and the central northern, midwestern, and the eastern mountain regions have elevated radon potential. You can see the EPA's radon potential maps and read more about how they were created here, on the EPA's website.
Structural Points of Entry
Crumbling and compromised building foundations can act as pathways whereby radon can leave the soil and enter homes. Evidence of cracking or crumbling can be a major red flag, as can other structural modifications typically associated with indoor moisture reduction. Unpaved basements, basement trenches, sumps, and drains are some structures that also allow radon to enter into homes and buildings.
Radon Mitigation Systems
If you notice ducts, pumps, vents and/or fans that aren't associated with building heating and air conditioning systems, they could possibly indicate a past or current radon problem. These items are associated with radon mitigation systems, mechanical systems put in place to reduce indoor radon concentrations. Although their presence might suggest that the problem has been fixed, this is not always the case. Many radon mitigation systems become ineffective over time, and systems that were never installed properly or are in disrepair due to age might not be able to remove radon to the degree that is required to protect human health. If present, radon mitigation systems should be functionally assessed.
Mechanical Systems that Reduce Indoor Air Pressure
Even a small drop in indoor air pressure can draw radon from the soil into one's home. This being the case, mechanical systems that artificially reduce pressure can be a big cause for concern. Two notable mechanical systems that can draw radon into buildings are sump pumps and elevators. Sump pumps can be very effective at bringing radon indoors and can cause major problems. If not properly sealed, their wells can act as a conduit for radon migration while their vacuum draws radon from beneath the basement slab. Likewise, the piston effect that occurs when elevator cars move between floors can act to create suction and distribute radon throughout a building.
Well Water
Although most significant indoor radon exposures come from soil, groundwater can contribute to exposure in some instances as well. Well water that is high in radon can release the toxic gas when used for cooking and showering activities. Unlike municipally water, which is typically treated for several days prior to distribution (a process which allows the naturally present radon to decay), well water usually travels directly from the groundwater source to the tap. As a result, this type of water can be several degrees of concentration greater that expected for municipally treated water. In instances where bathroom ventilation is poor, the radon gas can become trapped within the confines of bathrooms or kitchens leading to high levels of personal exposure.