Testing
Does a carbon monoxide detector detect radon?
Short answer
No. A carbon monoxide (CO) alarm is built to warn of a build-up of carbon monoxide, a gas from burning fuel, and a home air monitor detects only what it is designed for; a CO alarm has no way to sense radon. To measure radon you need a radon test kit or a radon monitor, read in picocuries per liter (pCi/L).
In brief
Two different gases, two different devices
A CO alarm and a radon test answer two different questions. Carbon monoxide is a colorless, practically odorless and tasteless gas from fuel that does not burn completely: in a furnace, a stove, a car or a generator. Radon is not made by anything in the house. It is an odorless, colorless, radioactive gas that comes from the natural decay of uranium and radium found in nearly all rocks and soils.
| Carbon monoxide (CO) | Radon | |
|---|---|---|
| What it is | A gas from incomplete combustion of fuel | A radioactive gas from uranium and radium in rock and soil |
| Where it comes from in a home | Fuel-burning appliances, vehicles and generators | The ground under the building, through openings in floors or walls |
| The harm | Can kill before you are aware it is in your home | Lung cancer, usually years later rather than immediately |
| What senses it | A CO alarm, certified to UL 2034 or IAS 6-96 | A radon test kit or a radon monitor |
| Unit a reading is given in | Parts per million (ppm) | Picocuries per liter (pCi/L) or becquerels per cubic meter (Bq/m3) |
What it is
- Carbon monoxide (CO)
- A gas from incomplete combustion of fuel
- Radon
- A radioactive gas from uranium and radium in rock and soil
Where it comes from in a home
- Carbon monoxide (CO)
- Fuel-burning appliances, vehicles and generators
- Radon
- The ground under the building, through openings in floors or walls
The harm
- Carbon monoxide (CO)
- Can kill before you are aware it is in your home
- Radon
- Lung cancer, usually years later rather than immediately
What senses it
- Carbon monoxide (CO)
- A CO alarm, certified to UL 2034 or IAS 6-96
- Radon
- A radon test kit or a radon monitor
Unit a reading is given in
- Carbon monoxide (CO)
- Parts per million (ppm)
- Radon
- Picocuries per liter (pCi/L) or becquerels per cubic meter (Bq/m3)
The CO alarm
What a carbon monoxide alarm is built to do
A CO alarm does one job well, and it is why the alarm belongs in every home. What it is built for:
- Warning of any unusual build-up of carbon monoxide in the home.
- Certification to the current Underwriters Laboratory (UL) Standard 2034 or the International Approval Services (IAS) 6-96 standard.
- Like a smoke detector, it is an emergency alert device, designed and certified to warn of a potentially life-threatening situation that needs attention right away.
- Placement on each level of the home, outside each sleeping area, as the U.S. Consumer Product Safety Commission recommends.
The sensor
Why a CO alarm cannot sense radon
Home air monitors detect only the pollutants or conditions they are designed for. A monitor built only to measure particles, for example, would not alert you to other harmful pollutants such as radon or carbon monoxide. The same holds the other way round: a CO alarm's sensor is made for carbon monoxide, and radon is a different gas.
The timing is different too. Unlike carbon monoxide and many other home pollutants, radon's health effect, lung cancer, usually does not appear right away, so a household can be exposed for many years without ever suspecting radon is there. An alarm that sounds in an emergency is the wrong tool for a risk that builds over years; what you need is a measurement of the average level.
The right tool
What does measure radon
You cannot see, smell or taste radon, so testing is the only way to know whether you and your family are at risk. The passive devices used for a home test are charcoal canisters, alpha-track detectors, charcoal liquid scintillation devices and electret ion chamber detectors; the active ones are continuous radon monitors and continuous working level monitors. Any of them, used as its instructions say, measures radon; a CO alarm is not on either list.
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.
Start with a short-term test in the lowest lived-in level of the home, run for at least 48 hours. Many states offer free or discounted kits: see free and low-cost radon test kits by state, or compare radon test kits and radon detectors.
FAQ
Carbon monoxide and radon questions
Will my carbon monoxide alarm go off if there is radon?
No. A CO alarm responds to carbon monoxide. A monitor detects only what it is designed for, and a CO alarm is not designed for radon. Only a radon test or radon monitor measures radon.
Is radon the same as carbon monoxide?
No. Carbon monoxide comes from burning fuel inside or near the home; radon is a radioactive gas from uranium and radium in the ground. They harm you differently and are measured differently, CO in parts per million and radon in pCi/L.
Which is more dangerous, radon or carbon monoxide?
They are dangerous in different ways. Carbon monoxide can kill before you know it is there. Radon's harm is lung cancer, which usually does not appear right away; EPA estimates radon is the second-leading cause of lung cancer in the United States. Protect against both: a CO alarm and a radon test.
Where should a CO alarm and a radon test go?
The Consumer Product Safety Commission recommends CO alarms on each level outside each sleeping area. A radon test goes in the lowest lived-in level of the home; the placement guide has the details.
Do I need a radon test if I have a CO alarm?
Yes. EPA and the Surgeon General recommend testing all homes below the third floor for radon, and a CO alarm cannot tell you your radon level.