Testing
Mold test vs radon test: what each one tells you
Short answer
They look for different things and work differently. A radon test measures a radioactive gas from the soil as a number in pCi/L you compare with EPA's 4 pCi/L action level, while a mold test is usually unnecessary when mold is visible, and there are no federal limits to compare a mold result with.
In brief
Mold and radon compared
| Mold | Radon | |
|---|---|---|
| What it is | Molds that grow where there is moisture | A radioactive gas from uranium and radium in rock and soil |
| Can you see or smell it? | Often, and if you see or smell mold, remove it | No: odorless and colorless |
| Is testing recommended? | CDC does not recommend mold testing; sampling is usually unnecessary if mold is visible | Yes: EPA and the Surgeon General recommend testing all homes below the third floor |
| Is there a number to compare with? | No federal limits for mold or mold spores | EPA's action level of 4 pCi/L |
| What fixes it | Clean up the mold and fix the moisture problem | A radon mitigation system, then a retest |
What it is
- Mold
- Molds that grow where there is moisture
- Radon
- A radioactive gas from uranium and radium in rock and soil
Can you see or smell it?
- Mold
- Often, and if you see or smell mold, remove it
- Radon
- No: odorless and colorless
Is testing recommended?
- Mold
- CDC does not recommend mold testing; sampling is usually unnecessary if mold is visible
- Radon
- Yes: EPA and the Surgeon General recommend testing all homes below the third floor
Is there a number to compare with?
- Mold
- No federal limits for mold or mold spores
- Radon
- EPA's action level of 4 pCi/L
What fixes it
- Mold
- Clean up the mold and fix the moisture problem
- Radon
- A radon mitigation system, then a retest
Mold
What a mold test does, and why it is rarely needed
In most cases, if mold growth is visible, sampling is unnecessary. No EPA or other federal limits have been set for mold or mold spores, so sampling cannot show whether a building meets a federal mold standard. Surface sampling can help show whether an area has been cleaned well enough, and it should be done by professionals with specific experience in mold sampling.
Mold affects different people differently, so sampling and culturing cannot tell you whether someone might become sick, and whatever type of mold is present, it needs to be removed. The key to mold control is moisture control: if mold is a problem, clean it up promptly and fix the water problem, and dry water-damaged areas within 24 to 48 hours to prevent mold growth.
Radon
What a radon test does, and why every home needs one
Radon is the opposite case: you cannot see it or smell it, so testing is the only way to know whether your family is at risk. EPA and the Surgeon General recommend testing all homes below the third floor for radon. The result is a number in picocuries per liter (pCi/L), and EPA recommends fixing a home when the radon level is at or above 4 pCi/L.
What does measure radon
Short-term radon test
Stays in the home two to 90 days, depending on the device, then goes to a lab. The usual first test.
Short-term kitsLong-term radon test
Stays in the home more than 90 days, so it is more likely to show your year-round average.
Long-term kitsContinuous radon monitor
Runs on power and usually gives hourly readings and an average for the test period.
Radon monitorsProfessional radon test
A qualified radon tester, very often a home inspector, places the device and reports the result.
Find a tester
Not sure which? The test chooser picks one for your situation, and many states give kits away: see free and low-cost kits by state.
Buying a home
Mold and radon during a home purchase
In a sale, hire a qualified radon tester, very often a home inspector; EPA recommends that an independent, qualified tester do the test. For mold, look for moisture and visible growth, and hire a professional with mold sampling experience only where sampling would answer a real question, such as whether an area has been cleaned well enough. Our radon and the home inspection guide covers how radon fits into an inspection.
FAQ
Mold test and radon test questions
Should I test for mold and radon at the same time?
Test for radon in every home below the third floor, as EPA and the Surgeon General recommend. For mold, testing is usually unnecessary: if you see or smell mold, remove it and fix the moisture.
Does mold cause radon, or radon cause mold?
No. Mold grows where there is moisture; radon comes from uranium and radium in rock and soil. One does not produce the other.
Is there a safe level for mold like there is for radon?
No federal limits have been set for mold or mold spores. For radon, EPA recommends fixing a home at 4 pCi/L or more, and considering a fix between 2 and 4 pCi/L.
Can one kit test for both mold and radon?
They are different measurements. A radon kit measures radon in pCi/L; read a combination product's specifications to see what it actually measures.