Radon: Forgotten but not gone
The news media did a great job of reporting on the dangers of radon in the 1990s. Now, you scarcely hear anything about it. But that doesn’t mean we shouldn’t continue to protect ourselves against this odorless gas that is the second leading cause of lung cancer among all people and the No. 1 cause of lung cancer among non-smokers.
People who live in mountainous or coal-heavy regions are at particular risk.
Many state codes mandate that builders of homes and some other types of dwellings install a passive radon mitigation system. Like any IAQ issue, there are two basic principles to minimize exposure. First is “source management,” and second is “dilution.” Dilution is such a favorite term that there is a saying among building science folks, “dilution is the solution.”
In essence, the builder lays a base layer of material, covered by plastic sheathing below the house. This material is sufficiently porous that any radon coming from the ground can be trapped, then vented through a PVC pipe passing through the sheathing on the ground, up through the house, exhausting over the roof line to open air. The heat from the house itself warms the pipe creating a natural draft, drawing the radon infused air up through the PVC chimney and away from the house. Where the gas is especially prevalent, an active component may need to be added in the form of a 100 cfm (cubic feet of air per minute) fan. This is considered a “source management” approach.
A “dilution solution” centers around in-house ventilation. By increasing the air change rate in the house you prohibit the radon gas from large build ups. There are three dilution strategies most commonly used: supply ventilation, balanced ventilation and exhaust ventilation. Each strategy has upsides and downsides. It’s recommended that you consult a professional as to which solution best fits your home design. And remember ventilation is different from circulation in that it moves fresh air from outside to in.
The maximum tolerable level of radon in a home or other building is 4 picocurie per liter of air during a 24 hour period, expressed as 4 pCi/L.
From an article published by Kansas State University:
A pCi is a measure of the rate of radioactive decay of radon. One pCi is one trillionth of a Curie, 0.037 disintegrations per second, or 2.22 disintegrations per minute. Therefore, at 4 pCi/L (picocuries per liter, the EPA's recommended action level), there will be approximately 12,672 radioactive disintegrations in one liter of air during a 24-hour period.
If you are unsure whether your home as a mitigation system, ask your builder or other building professional. You may also want to have your air tested.
Measurements should be taken by service providers trained or certified by the National Environmental Health Association, National Radon Proficiency Program or the National Radon Safety Board.
Even if your levels are satisfactory, there is no thing such as a completely safe radon presence. You can supplant any mitigation system by taking these steps recommended by the EPA:
- Air-seal sumps (e.g., install airtight sump cover) in such a way that water can drain from above and below the sump cover.
- Install airtight drain fittings (e.g., trap or flange system) in foundation floor drains.
- Seal and caulk penetrations, openings, or cracks in floors and below grade walls that contact the ground.
- Cover exposed earth floors in basements and crawlspaces.
By now, everyone knows that second-hand smoke kills. But it’s important to remember that your lungs are vulnerable to other kinds of carcinogens. Radon may be the most deadly of them, but with testing and some simple measures, the risks of harm can be greatly reduced.
Ken Nelson Ken Nelson is the Northwest Regional Sales Manager for the Panasonic Eco Products Division, specializing in ventilation solutions for residential and multi-family living environments. Over the past four years, Ken has spoken throughout the Northwest, teaching and training builders, building science advocates and professionals on the physics of moisture and air movement in homes of all sizes, types and age.