Skip to content
RADON411
$5

County radon report

Get it
Learn5 min read

Does radon have a smell?

By Radon411 Editorial TeamUpdated How we research

Short answer

No. Radon has no smell, color or taste, so you cannot detect it with your senses, and a musty, damp or rotten-egg smell in a basement is not a sign of radon; a radon test is the only way to know whether a home has a radon problem.

Next step: a test is the only way to know your home's level. How to test your home

Radon is an odorless, colorless and tasteless gas. That has a plain consequence: a home that smells fresh can have an elevated radon level, and a home with an odor problem may have a low one. Smell tells you nothing about radon either way.

Radon enters from the soil through cracks and other openings in the foundation and builds up indoors, usually most in basements, cellars and living spaces in contact with the ground. None of that produces anything you would notice day to day, and radon causes no immediate symptoms.

Because radon cannot be sensed, EPA recommends testing every home below the third floor, and testing is the only way to know whether you have a radon problem. The result, in (pCi/L), is what tells you whether to act.

What to do next: test the lowest lived-in level of your home, then read the result with the interpreter.

Why you cannot smell, see or taste radon

Radon is a naturally occurring noble gas that is odorless, colorless and tasteless. Nothing about it reaches the senses: you can't see it, smell it or taste it.

Radon and the senses
Can you…Answer
Smell it?No. It is odorless.
See it?No. It is colorless and invisible.
Taste it?No. It is tasteless.
Feel any symptoms from it?No. Radon's health effect is lung cancer, and most people have no symptoms until lung cancer is advanced.

The upshot is simple: a home that smells fresh can have a high radon level, and a home with a smell problem can have a low one. A smell tells you nothing about radon either way, and any smell in a home comes from something else.

How radon is found instead

Because people cannot sense radon, special equipment is needed to detect it. A radon test measures the gas, or the decay products it leaves, in the air of one room over a set time.

The kinds of radon testing devices
TypeExamplesHow it works
PassiveCharcoal canisters, alpha-track detectors, charcoal liquid scintillation devices, electret ion chamber detectorsNeeds no power; exposed to the air for a set time, then sent to a laboratory
ActiveContinuous radon monitors, continuous working level monitorsNeeds power; continuously measures and records radon or its decay products, usually with hourly readings
Table comparing a short-term radon test, a long-term radon test and a continuous radon monitor: how long each runs and what each is for.
Read this figure as text
TestHow long it runsWhat it is for
Short-term testStays in the home from 2 to 90 days, depending on the device, and for a minimum of 48 hours.A faster screening result. Because radon levels vary from day to day and season to season, it is less likely than a long-term test to tell you the year-round average.
Long-term testStays in the home for more than 90 days.It is more likely than a short-term test to tell you the home's year-round average radon level.
Continuous monitorLogs readings for the whole test, run as a short-term or a long-term test under the same durations in EPA guidance.Logs a graph over time, so you can see trends and spot anomalies rather than a single number.
Short-term tests, long-term tests and continuous monitors.

Where radon builds up without anyone noticing

Radon moves up from the soil and into a home through cracks and other holes in the foundation, and the home traps it inside, where it can build up. Levels are usually highest in basements, cellars and living spaces in contact with the ground, though considerable radon can be found above the ground floor too.

Cross-section drawing of a house with a basement and a crawl space, numbered at the seven ways EPA lists for soil gas to get in: cracks in solid floors, construction joints, cracks in walls, gaps in suspended floors, gaps around service pipes, cavities inside walls, the water supply.
Read this figure as text
House in cross-section showing where soil gas entersGround levelSoil and rockBasementSolid floorCrawl spaceSuspended floor1234567
  1. Cracks in solid floors
  2. Construction joints
  3. Cracks in walls
  4. Gaps in suspended floors
  5. Gaps around service pipes
  6. Cavities inside walls
  7. The water supply
The routes soil gas takes into a house. None of them comes with a smell.

Everyone breathes some radon every day, usually at very low levels. The concern is long-term exposure to higher levels indoors, which nothing in the air of the room will signal.

How common an unnoticed radon problem is

Because radon gives no sign, the only way to learn the level is a test, and high results turn up everywhere: high radon levels have been found in every state, and radon levels can vary greatly from one home to the next.

Radon levels for comparison
MeasureLevel
Average outdoor air, United States0.4 pCi/L
Average indoor air, United States1.3 pCi/L
Level at which EPA recommends considering a fix2 pCi/L
EPA's action level4 pCi/L

EPA estimates that nearly 1 out of every 15 homes in the U.S. has an elevated radon level. None of those homes smells any different.

Why a home that smells fine still needs a test

Without a smell or a symptom to go on, people fall back on guesses: the house is new, it has no basement, the neighbors tested low. None of those holds up, which is why EPA and the Surgeon General recommend testing all homes below the third floor.

Guesses people make about radon, and the facts
The guessThe facts
"Our house is new and well sealed."Any home may have a radon problem: new and old homes, well-sealed and drafty homes.
"We have no basement."Homes with or without basements can have a radon problem.
"The neighbors tested low."Radon levels can vary greatly from home to home; homes next to each other can have different levels.
"Radon isn't a problem around here."High radon levels have been found in every state.

A test is inexpensive and easy, and it should take only a few minutes of your time to set up. Place it in the lowest lived-in level of the home, in a room used regularly but not the kitchen or bathroom. See should I test for radon.

Questions about how radon smells

What does radon smell like?

Nothing. Radon is odorless, colorless and tasteless, so there is no smell to describe.

Does radon smell like rotten eggs, sulfur or must?

No. Radon has no smell, so a rotten-egg, sulfur or musty smell is coming from something else. It is worth tracking down on its own, but it is not a radon sign, and its absence is not an all-clear.

What does radon look like?

It doesn't look like anything: radon is a colorless, invisible gas.

Can you feel radon or get symptoms from it?

No. Radon causes no immediate symptoms. Its health effect is lung cancer, which may appear many years after exposure, and most people have no symptoms until it is advanced. See the symptoms of radon in your home.

Can a detector smell radon?

Not by smell. Radon detectors measure radioactivity: they record the amount of radon or its decay products in the air. See radon detectors.

Can you smell radon in water?

No. Radon in well water has no smell either; it is released into the air when the water is used for showering and other household uses. Test the air first, then the water if the air is high and you have a well.

Learn

Related guides

What radon is, where it comes from, how it gets indoors and what it does to health.

Everything in LearnOther guide topics
  • 17 min read

    Radon gas

    What it is, where it comes from and how it gets indoors.

    Read the guide
  • 17 min read

    Radon in homes

    How it gets in, where it builds up and what to do about it.

    Read the guide