I'm trying to lower radon gas levels at home.

I currently have one Airthings Wave Plus device in one room and I'm waiting for a second one to triangulate radon sources, but I'm looking for another hopefully faster way to solve this problem because the manufacturer says that to get a 10% accurate reading (no definition of "accurate") you need to leave the devices 7 days in the same place. Between that and the 24h rolling average charting they do, they feel like a clunky tool and the industrial tools I've seen are too expensive for what I'm trying to do.

Is there a way to "color" a gas, like radon that could let me temporarily see the house as a heatmap and identify where the gas is coming into the house?

  • From a number of reviews on the Big River shopping site, the Wave Plus looks like it could have significant accuracy issues for radon detection. I would certainly compare the readings from your unit(s) with those of known-good detectors placed in the same location. It would be a shame to spend a lot of effort based on wrong readings.
    – Armand
    Mar 24, 2022 at 11:41
  • 5
    Radon usually comes from the ground and is usually highest in basements below ground level. Basements usually have low air movement and the radon level tends to increase.
    – crip659
    Mar 24, 2022 at 12:05
  • 1
    @crip659 also building materials like concrete, brick and stone. And yeah, it collects where ventilation is non existent, usually basements. Out of curiosity, what kind of concentrations have you measured so far that you're concerned about radon? And at which location(s) in the house were these measured?
    – MiG
    Mar 24, 2022 at 14:03
  • 7
    even if somehow brightly colored, there's simply not enough radon molecules (even in a "high radon" area) to be visible to the human eye.
    – dandavis
    Mar 24, 2022 at 19:22
  • 6
    I think your idea is that there is a fault in the building which is letting the radon in, and that can be patched/sealed if identified. That isn't really practical, since concrete and stone is permeable to radon. Radon mitigation strategies generally involve "living with it", not "sealing anything" - i.e. improving air exchange in low places. Mar 24, 2022 at 20:02

5 Answers 5


Radon mitigation best practices are well defined - radon is heavy and tends to accumulate at the lowest point of the house where there is no ventilation.

Really I don't see much point in trying to find the source.

enter image description here

If you are in Andorra then your predicted radon levels are high and you should follow the best practices for radon mitigation. Air sealing and depressurization/ventilation of your sub slab. Don't have bedrooms in the basement / ground level. If you have radon gas you want to minimize the time you are exposed to it and sleep is likely the majority of your indoor time.

enter image description here

  • Another source of Radon is from granite; if you have granite mantle pieces or work surfaces then you should consider them as a source
    – CSM
    Mar 24, 2022 at 18:44
  • 7
    "radon is heavy and tends to accumulate at the lowest point of the house" -- this is misleading! The atomic mass of radon has virtually no effect here. Radon is found in low areas not because it is heavy, but because it comes from the ground. Its concentration remains higher in the basement due to slow mixing of indoor air, not gravity or buoyancy. Even in air with elevated radon levels, the actual amount of radon is minuscule, less than one part per quadrillion, so it has no noticeable effect on the air density. ...
    – nanoman
    Mar 25, 2022 at 0:24
  • 2
    ... In addition, even considering its large atomic mass, there is very little tendency for radon that is in the air to "settle out" and sink. See this answer and this comment.
    – nanoman
    Mar 25, 2022 at 0:25
  • According to this US Radon specialist (youtube.com/watch?v=ES_FNMQzy2U), and Canadian and WHO recommendations, the first thing you should do is measure Radon levels to see where hotspots are, hence my question. I also found this which shows how much of a difference different mitigation approaches help on average (tl;dr: active soil depressurization is by far the most effective): canada.ca/en/health-canada/services/publications/…. Mar 27, 2022 at 8:13
  • 1
    I watched the radon specialist video. The post construction radon mitigation installation technique was interesting. In your case, you know the area has high radon so the first thing I'd do is to depressurize the slab with ventilation and seal any penetrations. If after you've done that the radon is still high, add interior ventilation. I don't see the hotspot detection adding any real value. If you depressurize the slab, it would typically be the whole slab so it shouldn't matter where the hotspots are if there even is a difference. Mar 28, 2022 at 17:51

Radon is a noble gas and won't be affected by dyes like that.

You could rent a smoke machine and see how the air moves.

However the source of the smoke will be of your choosing. Not where the radon is emitting from.

Also the smoke tends to stink.

and if airflow is too low it's difficult to differentiate between natural dissipation and actual airflow.

  • Cheap alternative to a smoke machine maybe incense. At least that way you get to pick what it smells like...
    – keshlam
    Apr 5 at 12:02

There is no practical way to color Radon gas which enters the basement of a house.

But if a gas or oil burner, which depends on room air, is working in the basement, there would be a pretty high air exchange rate in the cold season. And also in the warm season, if the warm water is made by that burner.

The measuring results/triangulation in different locations could be misleading in this case, depending on the locations of the openings and the locations where Radon enters the basement.

Some modern burners do get their air via a double walled round stainless steel tube (inlet) chimney, in this case the air exchange rate in the basement is not affected.

Otherwise airing via (small) openings on opposite sides of a basement (west, east is optimal) should decrease the danger of accumulating Radon gas.

  • Assuming it's a basement-sourced burner. If it's direct-sourced, drawing combustion air from outside for better heating efficiency, you lose that forced ventilation.
    – keshlam
    Apr 5 at 12:04

Radon is produced in miniscule traces by radium. Radium is an alkali earth like calcium , very similar chemical properties. So if there is any radium it tends to be with calcium. Limestone is mostly calcium and may contain traces of radium. Some radium produces radon VERY,VERY slowly. Because it is a gas it seeps out cracks in the limestone, almost always with water. So water from a limestone formations is the source of radon. Ground water and well water from limestone may contain radon. A water sump in a basement is a possible source. The other most likely place in the shower if it is supplied from a limestone reservoir. The diagram from the Canada Natural Resourse shows this very well . Use the diagram to search for radon.


There are tools like Radon Sniffer which don't color gas but give you Radon levels in as little as 15secs but cost about $1750. It's too expensive for my purpose, but might be useful to others.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.