When you look at a house, most of the things you worry about are easy to understand. You can look at the roof, check the windows, ask about the heating system and have an inspector look for moisture or foundation problems.
Radon is different. You cannot see it, smell it or taste it. A house can look perfectly well maintained and still have an elevated radon level. The only way to know is to test.
That matters for anyone who owns a home in Prince Edward Island, but it can be especially important when a property is being bought or sold. A proper radon test takes time, and that does not always fit neatly into the schedule of a real estate transaction.
The good news is that testing is fairly simple, and if a home does have elevated radon, there are proven ways to reduce it.
What Is Radon?
Radon is a radioactive gas that occurs naturally when uranium in soil and rock breaks down. Outside, it normally disperses into the air and is not usually a concern. Inside a building, though, it can enter through cracks and openings around the foundation and build up to higher concentrations.
It can come in through cracks in concrete floors and walls, openings around pipes and drains, construction joints and other places where the building meets the ground. Differences in air pressure between the house and the soil underneath can help draw radon indoors.
That means the age or appearance of the house does not tell you whether there is a radon problem. An older home may have a low reading, while a newer home nearby may have a higher one.
Health Canada identifies long-term exposure to radon as an important cause of lung cancer. Canada’s guideline for indoor radon is 200 becquerels per cubic metre, or 200 Bq/m³. If a properly conducted long-term test comes back above that level, Health Canada recommends taking action to reduce the concentration.
Health Canada — Canada’s Radon Guideline
Health Canada — Take Action on Radon
Radon Can Be a PEI Issue Too
It can be tempting to think of radon as something that affects certain parts of Canada but not necessarily PEI. The problem with that approach is that radon levels can vary substantially from one home to another, even within the same neighbourhood.
The amount that enters a particular house depends on many things, including the soil underneath it, the foundation, the openings into the building and the way air moves through the home. That makes regional averages less useful than people sometimes expect.
The only reliable way to know the radon level in a particular home is to test it. That is really the most important point in the whole article. You do not need to guess based on the age of the house, where it is located or whether the neighbours have ever mentioned radon. You can measure it.
Health Canada — Take Action on Radon
Why Fall and Winter Are Good Times to Test
Radon levels do not stay exactly the same from day to day. They change with the weather, ventilation and the way a house is being used.
That is why Health Canada recommends long-term testing rather than relying on a short test taken over a few days. A proper test should run for at least 91 days, and current federal guidance says at least 91 days of the test period should fall during the heating season. Testing for three to twelve months gives a much better picture of the home’s average annual radon level.
Fall and winter are particularly useful because homes tend to be closed up more tightly. Windows and doors stay closed, ventilation can be lower, and the movement of warm air through the house can draw more soil gas inside.
That makes November a very good time to start. Someone who puts a detector in place now could have a useful long-term result during the winter or early spring, depending on the length of the test.
Health Canada — Guide for Radon Measurements in Homes
Where Should the Radon Test Go?
The detector should normally be placed on the lowest level of the home that people regularly use.
That distinction matters. If the basement is simply storage space that nobody spends much time in, the main floor may be the appropriate location. If the basement contains a bedroom, family room, home office or other space where someone spends four or more hours a day, the detector would normally be placed there.
Health Canada recommends keeping the device away from windows, exterior doors, heating vents and other areas where unusual airflow could affect the reading. It also needs to stay in place throughout the test. Normal day-to-day life should continue rather than changing how the house is heated or ventilated just because a test is underway.
The goal is to find out what people are actually breathing during normal use of the home.
Health Canada — Guide for Radon Measurements in Homes
Testing Is Something Most Homeowners Can Do Themselves
You do not necessarily need to hire someone to test your home.
Long-term do-it-yourself radon test kits are available, and the process is fairly straightforward. You place the detector in the appropriate part of the home, leave it there for the required period and then follow the instructions for getting the results.
PEI residents can also borrow radon detectors through the Provincial Library Service. The Province also directs Islanders to sources where radon test kits can be obtained, including the Lung Association of Nova Scotia and PEI and Take Action on Radon.
PEI Provincial Library Service — Specialty Library Items and Radon Detectors
PEI Government — Lung Health and Radon Testing
If you would rather have someone else handle the testing, Health Canada recommends using a radon measurement professional certified through the Canadian National Radon Proficiency Program.
Whichever approach you choose, the important part is doing a proper long-term measurement rather than treating a reading from a few days as the final answer.
Health Canada — Radon Gas: It’s in Your Home
What Happens if the Reading Is Above 200 Bq/m³?
First, don’t panic.
A reading above the Canadian guideline does not mean the house is suddenly unsafe to enter or that the property has somehow become worthless. Radon is a long-term exposure issue, and there are established ways to reduce it.
Health Canada recommends taking corrective action when the average annual radon concentration in a normally occupied area exceeds 200 Bq/m³. The higher the concentration, the sooner the work should be done.
Health Canada — Canada’s Radon Guideline
One of the most common methods is called active soil depressurization. In simple terms, a pipe and fan system draws radon-containing gas from underneath the foundation and exhausts it outside before it enters the home.
There are other measures that may help as well, including sealing certain cracks and openings, but the right approach depends on the building and the measured radon level. Simply opening windows or sealing a few visible cracks should not be treated as a permanent solution for a significant radon problem.
Health Canada recommends using a mitigation professional certified through the Canadian National Radon Proficiency Program. It reports that active soil depressurization is one of the most effective approaches and can substantially reduce radon concentrations.
Health Canada — Reducing Radon Levels in Your Home
After mitigation, the house should be tested again to make sure the system is working. Homes with active mitigation systems should also be retested periodically; current Health Canada guidance recommends retesting every five years where recent measurements are not available.
Health Canada — Guide for Radon Measurements in Homes
Radon Testing Can Be Awkward During a Home Purchase
This is where radon becomes particularly interesting from a real estate point of view.
A typical purchase may move from an accepted offer to closing in a matter of weeks. A proper long-term radon test takes at least three months. Those timelines simply do not match very well.
That means a buyer should not expect a normal home inspection to answer the radon question. An inspector may be able to point out conditions that deserve attention, but a home inspection cannot tell you the average annual radon concentration unless a proper test has already been completed.
Health Canada specifically advises against trying to conduct a long-term radon test during a normal real estate transaction. Its guidance suggests testing before selling or after purchasing because a three-month test generally does not fit within the usual buying and closing period.
Health Canada — Radon in Real Estate
A buyer can ask whether the seller has previously tested the property. If they have, ask for the results, when the test was done, how long it lasted and where the detector was placed. If there is already a mitigation system, ask for information about the installation and any follow-up testing.
If the house has never been tested, the most practical answer may simply be to plan a long-term test after moving in.
“When people buy a home, they naturally look at the things they can see — the roof, the foundation, the heating system and the general condition of the property. Radon is different because you can’t see it. Knowing whether a home has been tested is just one more piece of information that can help a buyer make a good decision.”
— Andrew Brown, Broker/Owner, CENTURY 21 Northumberland Realty
In some situations, buyers may want to discuss other arrangements with their REALTOR® and lawyer. Health Canada notes that some real estate transactions have used a holdback arrangement so testing and, if necessary, mitigation can take place after closing. That would need to be properly structured for the individual transaction rather than treated as a standard solution.
Health Canada — Radon in Real Estate
Sellers May Want to Test Before Listing
For sellers, timing can actually work in your favour.
If you are thinking about selling next spring, starting a radon test during the fall or early winter gives you time to get a meaningful result before the house goes on the market.
If the reading is low, you have useful information available if a buyer asks. If the reading is elevated, you also have time to investigate mitigation rather than discovering the issue in the middle of a sale.
A properly installed mitigation system, along with documentation and follow-up testing, can turn an unknown problem into something that has already been dealt with. Health Canada’s real estate guidance specifically encourages testing before selling where there is enough time to conduct a proper long-term measurement.
Health Canada — Radon in Real Estate
Sellers should keep copies of the radon test results, invoices and any documents connected with mitigation work. Questions about what must be disclosed in a particular sale should be discussed with the seller’s REALTOR® and lawyer rather than relying on a general rule.
A Newer Home Can Still Have Radon
It would also be a mistake to assume that radon only affects older houses.
Modern construction can include features designed to reduce radon entry or make future mitigation easier. New homes may have better sealing, improved foundation systems or provisions for a radon pipe.
Those features are useful, but they do not tell you what the actual radon concentration is inside the finished home. The same principle applies whether the house was built fifty years ago or last year: test rather than assume.
Health Canada’s current guidance recommends testing homes based on actual occupancy and indoor conditions rather than assuming that construction age or radon-resistant features guarantee a low result.
Health Canada — Guide for Radon Measurements in Homes
Pay Particular Attention to Finished Basements
Radon deserves extra thought when a basement is used as living space.
A storage basement that someone visits for ten minutes a day is very different from one containing two bedrooms, a television room and a home office.
If people spend several hours a day on the lowest level of the house, that is where their exposure matters most. Health Canada defines a normal occupancy area for testing as a space where someone spends more than four hours per day and recommends testing on the lowest lived-in level.
Health Canada — Guide for Radon Measurements in Homes
This is worth thinking about before finishing a basement as well.
Suppose you buy a bungalow with an unfinished lower level and plan to add bedrooms for the kids. Testing before you spend money on framing, flooring and finishes gives you the chance to include any radon work in the renovation if it is needed.
The same applies if you are planning a basement apartment or secondary suite. Renovations can change the way air moves through a home, so a significant change to the basement or ventilation can be a good reason to test again.
Don’t Forget to Retest After Major Renovations
A radon result is useful, but it does not necessarily last forever.
If you make major changes to the house, it can be worth testing again. New insulation, windows, ventilation equipment, foundation work or basement renovations can all change airflow through the building.
Health Canada recommends retesting after renovations or energy-efficiency work that may affect the structure or ventilation of the home. It also recommends continued testing of homes with active radon mitigation systems to make sure those systems are still working as intended.
Health Canada — Guide for Radon Measurements in Homes
Health Canada — Radon and Energy Retrofits
That does not mean you need to keep a radon detector running permanently. It simply means that when the house changes significantly, the conditions affecting radon may change too.
What Does Radon Mitigation Cost?
The cost depends on the size and design of the house and the type of work required, so it is better to get an estimate for the particular property than rely on a general number.
Health Canada’s current radon material says mitigation work typically costs in the same general range as other common home repairs, with a 2024 federal brochure citing approximately $2,000 to $4,000 as a typical range. That should be treated as broad Canadian guidance rather than a quote for work on a particular PEI home.
Health Canada — Reducing Radon Levels in Your Home
The important thing is to get estimates from certified radon professionals and find out what the particular house requires before making assumptions about the cost.
Five Questions Worth Asking About Radon
If you are buying, selling or simply wondering about your own home, there are a few straightforward questions that can help.
Has the house ever been tested? If it has, ask when the test was completed, how long it ran and what the result was.
Was the detector placed in the right location? A test in an unused corner of the basement may not represent the space where people actually spend their time.
Has the home changed since the test? Major renovations, new windows, insulation or changes to the heating and ventilation system can be reasons to test again.
If the result was high, was mitigation completed? Ask for documentation and follow-up results showing that the radon level was reduced.
If the house has never been tested, when are you going to do it? This is probably the most useful question of all.
The current Health Canada testing guide is a useful reference for all five questions because it covers test duration, placement, interpretation of results and when a home should be retested.
Health Canada — Guide for Radon Measurements in Homes
You Don’t Have to Guess
Radon is unusual because there may be absolutely nothing about the house that tells you it is there.
There is no stain on the wall. There is no strange smell. The furnace does not make a different noise.
That can make radon easy to ignore. But it also makes the solution fairly clear. Test the home, get a reliable long-term result and deal with the issue if the reading is elevated.
For buyers, that may mean asking whether testing has already been done and planning to test after moving in. For sellers, starting a test well before listing can remove some of the uncertainty before the property goes on the market. For people who simply plan to stay in their home, fall and winter are particularly good times to put a detector in place and find out.
Health Canada — Guide for Radon Measurements in Homes
Radon is invisible, but it does not have to remain an unknown.
