Radon Levels
Radon level of 5 pCi/L: is it bad?
Try it
Move a reading around 5 pCi/L
The reading starts at 5 pCi/L. Slide it to see where EPA's guidance changes and how far this number is from each line.
Read a result for 5 pCi/L
Starts at 5.0 pCi/L, this page's reading
EPA’s own thresholds, as its guidance states them.
EPA’s reading of 5.0 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 1.0 pCi/L above EPA's action level, 1.3 times it.
Short answer
Yes: a radon level of 5 pCi/L is above the 4 pCi/L action level, and once a follow-up test confirms it, EPA recommends fixing the home. There is no separate tier for 5 pCi/L; the guidance is the same as for any confirmed result at or above 4.
Next step: pick the right test for your home. Which test to use
Key takeaways
- 5 pCi/L is 1.25 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; 5 pCi/L is 3.85 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 5 pCi/L high?
On the risk chart, 5
- About 185 Bq/m3
- 5 pCi/L in becquerels per cubic meter, at about 37 Bq/m3 per pCi/L (calculated).
- 1.25 times
- EPA's 4 pCi/L action level (calculated).
- 3.85 times
- The U.S. indoor average of about 1.3 pCi/L (calculated).
Read moreThree paragraphs and a table, 1 min
If 5 pCi/L was a first short-term result, take a follow-up test to be sure, either long-term or a second
At about 185
Where 5 pCi/L sits against EPA's and WHO's reference points
Against outdoor air (about 0.4 pCi/L)
12.5 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, 6 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 5 pCi/L
EPA recommends fixing a home when the radon level is 4 pCi/L or higher. For a reading of 5 pCi/L, the steps come to this:
Steps for a reading of 5 pCi/L
Confirm it
If 5 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 5 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 5 pCi/L
EPA's risk chart has no row for 5 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
5 pCi/L sits between the 4 and 8 pCi/L rows, a quarter of the way from the lower row (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 185 Bq/m3, a long-term average of 5 pCi/L, that comes to about 30% 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 5 pCi/L?
A first short-term result of 5 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 5 pCi/L, a year-round average a third lower would be 3.33 pCi/L, just under the
Read moreA note, 1 min
With a system
How much a radon system would lower 5 pCi/L
From 5 pCi/L, an active system at the low end of its typical range would leave about 2.5 pCi/L, inside the 2 to 4 pCi/L range; at the high end, about 0.05 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 5 pCi/L, about |
|---|---|---|
| Active suction: sub-slab, sump hole, drain tile, or a crawl-space membrane | 50 to 99 percent | 2.5 to 0.05 pCi/L |
| Passive sub-slab suction (no fan) | 30 to 70 percent | 3.5 to 1.5 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 5 pCi/L
5 pCi/L in three common situations
5 pCi/L on a first short-term test
Confirm it before deciding, with a long-term test or a second short-term test. The decision rests on the long-term result, or on the average of the two short-term results.5 pCi/L in a basement you have started using
When you begin occupying a lower level such as a basement, retest on that level. Levels are usually higher in rooms in contact with the ground.5 pCi/L after a renovation
Major renovations can change the radon level in any home, so test again once the work is done, in the lowest lived-in area.
Retest
When to retest after 5 pCi/L
5 pCi/L is 1 pCi/L over the action level (our calculation): over the line, but close enough that a single short-term test is less definitive. Either follow-up works. A long-term test gives the year-round answer; a second short-term test gives the quicker one.
| 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 5 pCi/L: questions
Is 5 pCi/L of radon safe?
No. 5 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 5 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; 5 pCi/L is 1.25 times that line.
What is 5 pCi/L in Bq/m3?
It is about 185 Bq/m3, at about 37 Bq/m3 per pCi/L (our calculation).
Should I buy a house with a radon level of 5 pCi/L?
A high level is fixable: from 5 pCi/L, an active system's typical reduction would leave 2.5 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 5 pCi/L in a basement different from upstairs?
Usually the basement reads higher. If 5 pCi/L came from a room upstairs, a basement half again as high would read 7.5 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 5 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: 5 pCi/L is 1 pCi/L over the line.
Can a system bring 5 pCi/L under 2?
Often. With today's technology radon levels in most homes can be reduced to 2 pCi/L or below. From 5 pCi/L that is a cut of 60 percent (our calculation), inside the 50 to 99 percent typical of active soil suction.