Canadian Association of Radon Scientists and Technologists

Helping Canadians Reduce Radon Risk

Testing for Radon during a Real-Estate Transaction?  

Here are some things to consider.


    Testing is easy and it should be done in the living area of the home.

Tests should be done for at least 91 days.    

  Radon enters buildings where they touch the ground.

Every house can be reduced to a safe radon level: 

Call a trained professional to help:

Every home needs to be tested and all 

homes can be fixed.


Radon is killing 3200 Canadians per year from lung cancer.

Radon is the leading cause of lung cancer in non-smokers.

The cost of a radon mitigation system is not expensive.

It is less costly than other home renovations.


Resources about RADON and REAL ESTATE:

Real Estate Infograph 

Realtor Information

Radon Presentation (pdf) Radon Presentation (powerpoint) 
Radon Backgrounder for Real Estate Agents 
Webinar for Real Estate Agents

French Resources:

Real Estate Infograph - FRENCH.pdf

Radon dans le cadre d’une transaction immobili√®re

Understanding how a Radon Assessment fits into your 

Real Estate Transaction

Here's how an assessment during a real-estate transaction works:
First, contact a C-NRPP Measurement Professional to conduct a Radon Screening Assessment for you.
The occupant of the home must agree to the test, and also to keeping the home under 'closed house' conditions for as long as required.
Closed-house conditions include: 
  • Windows should stay closed at all times, 
  • External doors opened only for entry and exit,
  • Attached garage doors should be opened only for entry and exit,
  • Fireplaces should not be operated during the radon test, unless they are the primary heat source.
  • Clothes dryer, range hood, and bathroom fan operation should be limited to the minimum necessary,
  • Radon mitigation systems shall be operated as normal.
  • Heat-Recovery Ventilator (HRV) and Energy Recovery Ventilator (ERV) shall be left to operate (or not operate) as found.  For example, if an HRV is plugged in and working it should be left working, if unplugged, should be left unplugged.
The Radon Screening Assessment will be set up by the C-NRPP Measurement Professional.  The detector must be in place for a minimum of 4 days.  A longer duration is preferred, but not always practical in a real estate situation.

The C-NRPP Measurement Professional has specific guidelines about where and how to place the test, as well as how to report on the results.  This may include using 2 detectors, depending on the type of devices used.

Understanding my Radon Assessment Report

The Radon Assessment Report will provide a result of Green, Yellow or Red to help you understand the likelihood that the annual average radon concentration could be above 200 Bq/m3.  

Green Test Result

A Green Test Result indicates a radon screening assessment of 75 Bq/m3 or less during the heating season and 50 Bq/m3 or less outside the heating season.   It is important to note that a “Green” test does not guarantee that the annual average radon concentration in the dwelling is below 200 Bq/m3. A long-term follow-up radon measurement conducted during the next heating season must still be carried out.

Yellow Test Result

A Yellow Test Result indicates a radon screening assessment of greater than 75 Bq/mduring the heating season or 50 Bq/m3 outside the heating season, up to and including 400 Bq/m3.  This result indicates that there is a higher likelihood that the annual average radon concentration is above 200 Bq/m3

Red Test Result

A Red Test Result indicates a radon screening assessment of greater than 400 Bq/m3. This result indicates a strong likelihood that the annual average radon concentration is above 200 Bq/m3

Do I Need to Worry About Newly Built Homes?

New homes are not radon free. Some new homes feature radon resistant features, but these does not guarantee low levels. Testing is ALWAYS recommended when occupying a new space. 

Ontario Homes are covered under the Tarion warranty which provides free mitigation when radon levels are above Canada's guideline within the first 7 years of the home being constructed.  Find more information here.

Frequently Asked Questions:

Q.  Health Canada suggests testing for at least 3 months.  Why does this document suggest a 4 day test?

A. Every home needs to be tested for radon using a long-term (3 months+) test.  This guideline offers an additional test that can be performed during a real-estate transaction, in the case where the home had not already been tested for radon prior to being listed for sale. 

Due to the time constraints frequently experienced during a real estate transaction, long-term radon measurements are often not practical during the time a house is for sale.  If a long-term radon measurement has not been conducted prior to a real estate transaction, a radon screening assessment can provide important information on whether funds may be required to cover the installation of a radon mitigation system.  It’s important to remember that even after a home has been assessed using a radon screening assessment, it must still be tested using a long-term radon test once the new owners take possession of the house.

Q.  We’ve lived in our home for many years.  Why should we test our home now, when we’re selling it?

A. Radon is a health hazard that Canadians have become increasingly aware of over the past few decades.  Every home needs to be tested for radon, as it’s the only way to know the radon level in the home and whether the level should be reduced.  Just as the home inspection will let the prospective buyer know about upcoming expenses, the radon screening assessment will let them know whether they’re likely to have the expense of installing a radon mitigation system.  It is important to budget funds to take care of such an important health concern. 

Q. Will the radon assessment test slow the sale of our home or ruin the transaction?

A. More and more Canadians are including a radon test as part of buying a home.  In some areas every home is tested for radon prior to being sold.  CARST’s Guideline sets out the best way to include radon in the real-estate transaction while considering everyone involved.  Just like an old furnace or roof shingles in need of repair, high radon levels are easily remedied, at a price point that can be included in the negotiations.  Following this guideline means that everyone involved in the sale of your home is “on the same page” and misunderstandings are less likely to occur.

Q. How much does a radon mitigation cost?

A. The cost of radon mitigation varies depending on the type of house construction, the type of mitigation system required, the location of the home, and market trends.  It is difficult for a non-professional to assess the various factors that will determine how difficult it is to mitigate a given home.  It is therefore important to obtain a quote from a C-NRPP mitigation professional when budgeting for the cost of mitigation.  While the majority of mitigations across Canada range in price from $2 000 to $4 000, the cost may occasionally be as high as $10 000. 

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