Radon Levels
Radon level of 6 pCi/L: what it means and what to do
Try it
Move a reading around 6 pCi/L
The reading starts at 6 pCi/L. Slide it to see where EPA's guidance changes and how far this number is from each line.
Read a result for 6 pCi/L
Starts at 6.0 pCi/L, this page's reading
EPA’s own thresholds, as its guidance states them.
EPA’s reading of 6.0 pCi/L
At or above 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. That is 2.0 pCi/L above EPA's action level, 1.5 times it.
Short answer
A radon level of 6 pCi/L is high by EPA's standard: it is 1.5 times the 4 pCi/L action level, and once it is confirmed the home should be fixed. Readings of 6 to 7 pCi/L call for the same steps.
Next step: pick the right test for your home. Which test to use
Key takeaways
- 6 pCi/L is 1.5 times EPA's 4 pCi/L action level.
- At or above EPA's action level: fix once confirmed.
- EPA estimates the average U.S. home at about 1.3 pCi/L; 6 pCi/L is 4.62 times that.
- Confirm a short-term result with a second test; a long-term test shows the year-round average best.
Where it sits
Is a radon level of 6 pCi/L high?
On the risk chart, 6
- About 220 Bq/m3
- 6 pCi/L in becquerels per cubic meter, at about 37 Bq/m3 per pCi/L (calculated).
- 1.5 times
- EPA's 4 pCi/L action level (calculated).
- 4.62 times
- The U.S. indoor average of about 1.3 pCi/L (calculated).
Read moreThree paragraphs and a table, 1 min
Because 6 pCi/L is less than twice the
6 pCi/L is about 222
Where 6 pCi/L sits against EPA's and WHO's reference points
Against outdoor air (about 0.4 pCi/L)
15 times the outdoor average (calculated)Against WHO's recommended reference level (100 Bq/m3, 2.7 pCi/L)
Above itEPA's band
At or above EPA's action level: fix once confirmed
Other readings explained: 1 pCi/L, 2 pCi/L, 3 pCi/L, 4 pCi/L, 5 pCi/L, 7 pCi/L, 8 pCi/L, 10 pCi/L, 12 pCi/L, 20 pCi/L, 30 pCi/L, 100 pCi/L.
What to do
What to do about a radon level of 6 pCi/L
EPA recommends fixing a home when the radon level is 4 pCi/L or higher. For a reading of 6 pCi/L, the steps come to this:
Steps for a reading of 6 pCi/L
Confirm it
If 6 pCi/L was a first short-term result, take a follow-up test: a long-term test for the year-round average, or a second short-term test if you need results quickly.Decide on the confirmed number
EPA recommends fixing a home when the radon level is 4 pCi/L or higher. The decision rests on one long-term test or the average of two short-term tests: two results averaging 6 pCi/L call for the fix.Hire a qualified contractor
Get more than one estimate and a written contract; see radon mitigation.Test after the fix
No sooner than 24 hours and within 30 days after the system starts, then at least every two years.
Read moreA paragraph, 1 min
The full sequence of tests, from a first result to the decision to fix, is drawn on radon testing.
Health risk
The lung cancer risk at 6 pCi/L
EPA's risk chart has no row for 6 pCi/L, so the table shows the rows either side of it. The chart estimates how many people out of 1,000 could get lung cancer if exposed to a level over a lifetime, for people who smoked and people who never smoked.
| Radon level | People who smoked | People who never smoked | What to do |
|---|---|---|---|
| 8 pCi/L (300 Bq/m3) | About 120 in 1,000 | About 15 in 1,000 | Fix your home |
| 4 pCi/L (150 Bq/m3) | About 62 in 1,000 | About 7 in 1,000 | Fix your home |
Read moreTwo paragraphs, 1 min
6 pCi/L sits between the 4 and 8 pCi/L rows, halfway between them (our calculation). At 8 pCi/L the chart gives about 120 in 1,000 people who smoked (30 times the risk of dying in a fall), and about 15 in 1,000 who never smoked (4 times the risk of dying in a fall); at 4 pCi/L, about 62 in 1,000 people who smoked (5 times the risk of dying in a car crash), and about 7 in 1,000 who never smoked (the risk of dying in a car crash).
Lung cancer risk is estimated to rise by about 16% per 100 Bq/m3 of long-term average radon. At 220 Bq/m3, a long-term average of 6 pCi/L, that comes to about 35% above the risk with no radon at all (our calculation, a population estimate, not a forecast for one person); a former smoker's risk may sit between the chart's two columns.
How sure
How certain is a reading of 6 pCi/L?
A first short-term result of 6 pCi/L is enough to act on only once a second test agrees: radon varies from day to day and season to season, and a long-term test is likelier to show the year-round average. At 6 pCi/L, a year-round average a third lower would be 4 pCi/L, still at or above the action level.
Read moreA note, 1 min
With a system
How much a radon system would lower 6 pCi/L
From 6 pCi/L, an active system at the low end of its typical range would leave about 3 pCi/L, inside the 2 to 4 pCi/L range; at the high end, about 0.06 pCi/L. Our arithmetic on the published ranges, not a prediction for your house: radon levels in most homes can be reduced to 2 pCi/L or below.
| Technique | Typical reduction | From 6 pCi/L, about |
|---|---|---|
| Active suction: sub-slab, sump hole, drain tile, or a crawl-space membrane | 50 to 99 percent | 3 to 0.06 pCi/L |
| Passive sub-slab suction (no fan) | 30 to 70 percent | 4.2 to 1.8 pCi/L |
Read moreA paragraph, 1 min
Which technique fits depends on the foundation; see radon mitigation systems, and for cost, radon mitigation cost.
Situations
Where people meet a reading of 6 pCi/L
6 pCi/L in three common situations
6 pCi/L on a first short-term test
Take a second short-term test if you want a quick decision, or a long-term test, more than 90 days, for the year-round average.6 pCi/L in a home sale
The buyer and seller should discuss the timing and costs of radon reduction, and write into the contract when mitigation will be done and who will pay for it.6 pCi/L after a mitigation system
As a post-mitigation result, 4.0 pCi/L or greater means fix the building, and with a system already installed, more work may be needed to lower the radon further. Many contractors guarantee to adjust or modify the system to reach a negotiated level, so start with that guarantee.
Retest
When to retest after 6 pCi/L
6 pCi/L is 1.5 times the action level but less than twice it, so the rule for an immediate second short-term test, a first result more than twice 4 pCi/L, does not apply. The higher the first result, though, the more certain you can be that a short-term follow-up, rather than a long-term one, is right.
| When | What to do |
|---|---|
| To confirm the first result | With a long-term test, or a second short-term test if you need results quickly |
| After a system is installed | No sooner than 24 hours and within 30 days, with a two- to seven-day test |
| With a system in place | At least every two years |
| After a remodel | In the lowest lived-in area |
Show all 4 rows
Read moreA paragraph, 1 min
The general answer is on how often should I test for radon.
Questions
Radon level of 6 pCi/L: questions
Is 6 pCi/L of radon safe?
No. 6 pCi/L is at or above EPA's 4 pCi/L action level, where EPA recommends fixing the home once the result is confirmed.
Do I need radon mitigation at 6 pCi/L?
Yes, by EPA's guidance, once a long-term test or the average of two short-term tests confirms the level is 4 pCi/L or more; 6 pCi/L is 1.5 times that line.
What is 6 pCi/L in Bq/m3?
It is about 220 Bq/m3, at about 37 Bq/m3 per pCi/L (our calculation).
Should I buy a house with a radon level of 6 pCi/L?
A high level is fixable: from 6 pCi/L, an active system's typical reduction would leave 3 pCi/L or less. Buyers and sellers should discuss the timing and costs of radon reduction, and the contract can say when mitigation happens and who pays. See should I buy a house with radon.
Is 6 pCi/L in a basement different from upstairs?
Usually the basement reads higher. If 6 pCi/L came from a room upstairs, a basement half again as high would read 9 pCi/L, at or above the action level; a test belongs in the lowest lived-in level.
How long should I wait to retest after 6 pCi/L?
Follow up soon, with a long-term test if you have time or a second short-term test if you need results quickly: 6 pCi/L is 2 pCi/L over the line.
What would a system leave from 6 pCi/L?
At the low end of the 50 to 99 percent typical of active soil suction, about 3 pCi/L or lower (our calculation). Only a test after installation shows what a system achieved.