Radon in Your Home

What is radon?

Radon is a naturally occurring radioactive gas released when uranium in soil and/or rock breaks down. Radon is invisible, odourless and tasteless. Radon does not tend to be a health issue outdoors, as atmospheric mixing dilutes the gas to low concentrations. However, in a confined space - like a basement - radon can accumulate to elevated levels, which can present a health risk.

How can I be exposed?

Radon can seep into a building through dirt floors, cracks in foundations or concrete, sump pumps, joints and basement drains. Well water can also contain trapped radon, which may be released into the air when water is drawn.

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Radon can seep into a building through dirt floors, cracks in foundations or concrete, sump pumps, joints and basement drains. Well water can also contain trapped radon, which may be released into the air when water is drawn.

Radon concentrations vary a great deal across Canada, and within the City of Ottawa, making it difficult to predict radon levels in any one home or building. Radon levels are generally higher in areas where there is a higher amount of uranium in underlying rock and soil and may be higher in homes that have been made more airtight without also ensuring that the fresh air supply is sufficient.

What are the health implications?

When a radioactive gas, like radon, is inhaled, it naturally breaks down into radioactive particles that can be trapped in your lungs when you breathe in. This may cause damage to lung tissue, which can develop into lung cancer over the course of a lifetime.

The health risks from radon exposure are long-term and often depend on three things:

  1. The level of radon in your home or building
  2. The length of time you are exposed to radon
  3. Your smoking habits or exposure to second-hand smoke

What can I do?

The only way to know if you are being exposed to radon gas is to test for it. Testing for radon is easy and affordable. Health Canada suggests that you use a long-term radon detector for a minimum of three months.  

If you are building a new home, the Ontario Building Code requires your builder to include a soil gas barrier and a heat recovery ventilator. The soil gas barrier is a layer of protective material that prevents radon entering buildings. The heat recovery ventilator (HRV), also known as fresh air exchangers, remove excess moisture and indoor pollutants (radon, mould, household chemicals and bacteria) and let fresh air inside while using the exhausting air to warm the incoming air.  

In addition to these building code requirements, you can ask your builder to install a portal for a sub-slab depressurization system that can divert soil gases such as radon from entering your home.  Should a post-occupancy radon test determine radon gas levels are elevated, sub-slab depressurization is recommended to lower radon gas levels indoors 

If you live in a newly built home, you should be aware that the Tarion New Home Warranty considers elevated levels of radon gas be considered as major structural defect as an environmentally harmful substance or hazard. For information on radon in a new home please visit the Tarion website.

There are two options to test buildings for radon:

  1. Do-it-yourself radon test kit
    • Can be purchased over the internet, at local hardware, home improvement, or building supply stores (Currently Ottawa Public Health does not have any kits for sale)
    • The cost of testing ranges from $29 to $170
    • Find a Radon Test Kit Provider Near You: https://takeactiononradon.ca/test/radon-test-kits/
  2. Hire a radon testing company

What are the acceptable concentrations?

The  Health Canada guideline for radon in indoor air for dwellings is 200 Becquerels per cubic metre, or less.

How can I fix my radon problem?

If a long-term (three months to six months) radon detection test shows a living or active space to be above the Canadian guideline of 200 Becquerels/m3, Health Canada and Ottawa Public Health recommend that home or building owners consult a certified radon professional to determine the best radon reduction plan to lower radon levels. The concentration of radon gas will determine how quickly you should lower your radon exposure - the higher the level of radon gas in a building, the faster you should take action to reduce your exposure.

How soon to take action to reduce the radon level?

>600 Bq/m³

200 - 600 Bq/m³

Remediate within one year

Sick house

Remediate within two years

Sad house

Contact the Canadian National Radon Proficiency Program at 1-855-722-6777 or visit the following website for a list of certified radon professionals who can help reduce the level of radon in your home.



Contact information

For more information call Ottawa Public Health at 613-580-6744.

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