Radon Testing When Buying or Selling a Home in Canada (2026): A Buyer's, Seller's, Realtor's & Lawyer's Guide

A note before you read. This article is general educational information for Canadian homeowners, buyers, sellers, and real-estate professionals. It is not legal, professional, or warranty advice, and it is not a substitute for advice from a qualified real estate lawyer in your province. Laws, regulator guidance, and standard form language change. Always verify the current rule in your jurisdiction with a qualified professional before relying on any of the information below in a transaction. See the full disclaimers at the bottom of this article.

Radon is the single most overlooked health issue in Canadian real estate transactions. Most home inspectors don't test for it, most standard purchase agreements don't mention it, and most buyers and sellers don't think to ask — even though Health Canada attributes roughly 3,200 Canadian lung cancer deaths every year to radon, the leading cause of lung cancer in non-smokers. (Health Canada, CARST)

For the four people who actually move a transaction — buyers, sellers, realtors, and real estate lawyers — radon is also a legal exposure that has crystallized fast in the past three years:

• Radon levels above 200 Bq/m³ are a "material latent defect" that must be disclosed in writing under the express guidance of the provincial real estate regulators in BC (BCFSA) and Alberta (RECA). Other provinces apply the latent-defect doctrine through case law and provincial real-estate regulator guidance — the underlying disclosure obligation exists, though the "in writing" formality varies.
• Canadian courts have treated radioactive contamination as a latent defect triggering a positive duty to disclose, even where the general rule of caveat emptor applies. The leading case (Sevidal v. Chopra, Ont. H.C.J. 1987) involved radioactive soil contamination near a residential property and is regularly cited by analogy in radon-related disclosure analysis.
• Failing to disclose can unwind a deal or trigger damages claims years later — the appropriate remedy depends on the facts, the agreement, and provincial limitation rules.
• The right test, used the right way, can also create real upside: in Ontario, on a home whose Agreement of Purchase and Sale was signed on or after February 1, 2021 and is within its 7-year warranty window, a long-term result above 200 Bq/m³ can trigger up to $50,000 of builder-funded mitigation under Tarion. (Tarion radon coverage)

This guide is written for the four people who actually need to act: buyers, sellers, realtors, and real estate lawyers. It walks through the legal framework, the practical playbooks, the closing-window options when you can't run a 91-day test, and the mistakes that turn a small problem into a large one.

TL;DR — by role

• Buyer: Ask before you offer. If the seller has tested, demand the lab report. If not, write in either a conditional offer with a CARST short-term Real Estate Screening Assessment, a mitigation holdback, or both — then run a long-term test post-possession. Order a long-term post-possession kit — $89 →
• Seller: If you have ever tested and the result was above 200 Bq/m³ and you have not mitigated, your real estate lawyer will likely advise you to disclose in writing — BC and Alberta regulators treat this as a material latent defect, and the latent-defect doctrine applies in other provinces through case law. If you mitigated, the express disclosure rule generally falls away in BC and Alberta — but you must still answer truthfully if asked. Pre-listing testing is a defensive move that prevents nasty surprises. Test pre-listing — $89 →
• Realtor: Ask sellers and listing agents directly: Has the home been tested? Can I see the lab report? In writing. Document your file. Recommend testing to buyer clients and document that recommendation, even when they decline. Standard CARST scripts and BCFSA checklists are linked below.
• Real estate lawyer: This is increasingly an issue you'll see on closing files. Standard mitigation-holdback clauses, post-closing testing periods, and a disclosure-evidence trail (lab report on letterhead from a C-NRPP-certified Canadian lab) protect your client whether they're buying or selling.

Table of contents

1. Why radon shows up in real estate transactions
2. The Canadian legal framework: caveat emptor, latent defects, and Sevidal v. Chopra
3. Province-by-province disclosure rules
4. The buyer's playbook
5. The seller's playbook
6. The realtor's playbook
7. What your real estate lawyer will want to see
8. The CARST Real Estate Screening Assessment (4–7 day test) — what it is and isn't
9. Mitigation holdbacks: how they actually work
10. Special situations (new builds, Tarion resale transfer, rentals, mitigated homes)
11. What to do after closing — the long-term follow-up test
12. FAQ
13. Disclaimers
14. Sources

Why radon shows up in real estate transactions

Radon is a naturally occurring radioactive gas produced by the breakdown of uranium in soil and rock. It enters homes through cracks in foundations, gaps around service penetrations, sump pits, and crawl spaces, and accumulates indoors — especially in basements during the heating season. Health Canada's published guideline is 200 Becquerels per cubic metre (Bq/m³), above which corrective action is recommended. (Health Canada — Guide for Radon Measurements)

A few facts that matter to a transaction:

• Health Canada's most recent national survey found roughly 7% of Canadian homes test above the guideline on average — but the figure varies sharply by region, exceeding 20% in some provinces and health regions. No region of Canada is "low risk" — two homes side by side can have very different radon levels. (CREA Homeowner's Guide, Health Canada — Cross-Canada Survey of Radon Concentrations)
• Radon is odourless and invisible. A pre-purchase home inspection will not detect it. Buyers will not "find out later" by themselves — they have to test.
• Mitigation works: a properly installed sub-slab depressurization system can reduce radon by up to 95% and typically costs $2,500–$4,500 in Canada (occasionally more for complex homes). (CREA / CARST)
• The cheapest moment to deal with radon is before closing, when the cost is on the table for negotiation. The most expensive moment is the day after, when it's entirely the buyer's problem.

That last point is what this article is about.

The Canadian legal framework: caveat emptor, latent defects, and the Sevidal line

(This section is general legal information for context, not legal advice. See disclaimers.)

Canadian residential real estate operates on the default rule of caveat emptor — buyer beware. Buyers are generally responsible for inspecting and informing themselves before purchasing. (Aaron & Aaron — Caveat emptor)

But caveat emptor is not absolute. Canadian courts have carved out exceptions, the most important of which (for radon) is the latent defect doctrine.

Patent vs. latent defects

A patent defect is one a reasonable buyer could see during an ordinary inspection — peeling paint, a cracked window, a sloping floor. The buyer is on notice and caveat emptor applies fully.

A latent defect is hidden from ordinary inspection — for example, contamination beneath the slab, structural defects behind drywall, or a radioactive gas with no smell or colour. Where a seller knows about a latent defect that renders the property dangerous or unfit for habitation, the seller has a positive duty to disclose. (Sullivan Mahoney — Law of Latent Defect)

Sevidal v. Chopra and the radioactive-contamination disclosure line

In Sevidal v. Chopra (Ontario, 1987), the Ontario High Court of Justice considered radioactive soil contamination in a residential neighbourhood and held that it constituted a latent defect — and because it was potentially dangerous, the seller had a duty to disclose it to buyers. Sevidal is one of several Canadian decisions cited in commentary on the latent-defect doctrine and is regularly invoked as a starting point for radioactive-contamination disclosure analysis, including by analogy to elevated indoor radon. (CanLII — Caveat Emptor and the Sale of Land, Sullivan Mahoney — Law of Latent Defect)

The "material latent defect" rule, made explicit by provincial regulators

Real estate regulators in multiple provinces have now made the radon-disclosure rule express:

• British Columbia — BCFSA's Radon Precautions Guidelines state plainly: "If you learn from the seller or landlord that the home has been tested and the radon levels exceed 200 Bq/m³, this is a material latent defect and you must disclose this information to potential buyers or tenants." Disclosure must be in writing. (BCFSA Radon Precautions Guidelines)
• Alberta — RECA states: "If a radon test shows high levels of radon (higher than 200 Becquerel), that's considered a material latent defect that MUST be disclosed to prospective buyers unless a radon mitigation device is installed prior to listing." (RECA — Property Considerations · RECA Radon Information Bulletin)
• Quebec — OACIQ requires brokers to ask sellers about prior radon tests and remediation, and to disclose past expert results to prospective buyers (clauses D12.1, D12.2, D13.9 of the Declarations by the seller of the immovable form, mandatory since 2012). Quebec courts have treated elevated radon as a defect requiring disclosure. (OACIQ Radon Guide)
• Ontario — OREA's Form 220 (Seller Property Information Statement, "SPIS") includes environmental concerns. SPIS use is voluntary, but once a seller completes one — or once a seller has tested — the duty to answer truthfully and the latent-defect doctrine apply. (Larson Lawyers on SPIS)
• Other provinces — most use province-specific Property Disclosure Statements and follow the same latent-defect framework. The federal real estate body (CREA) and CARST jointly publish a Homeowner's Guide to Radon circulated to its 117,000 REALTOR® members. (CREA Homeowner's Guide to Radon)

What removes the disclosure obligation

Important nuance: in BC and Alberta, regulators have stated expressly that once mitigation is installed and the home is brought below 200 Bq/m³, the prior elevated reading is no longer a "material latent defect" that must be voluntarily disclosed. (BCFSA, RECA)

In Ontario, Quebec, and other provinces without an express regulator rule on point, the law on continuing post-mitigation disclosure of prior elevated readings is less developed. Best practice (and what your real estate lawyer will likely recommend) is to continue to disclose the mitigation history voluntarily, supported by mitigation documentation and a post-mitigation lab report — both because it removes uncertainty and because it positions the home as better-than-untested, not worse-than-clean.

But — and this matters — a real estate licensee must still answer truthfully if directly asked. "Has this home ever had elevated radon?" is a question with only two professional answers: a truthful "yes, and here's the mitigation documentation," or a refusal to answer (which any sophisticated buyer reads as a yes anyway). Lying or omitting in response to a direct question can give rise to professional discipline against the licensee and may give grounds to seek rescission of the transaction or damages, depending on the facts. (BCFSA Radon Precautions Guidelines)

It is also worth noting that no boilerplate "as-is" or "no representations" clause overrides a seller's positive duty arising from fraudulent concealment of a known dangerous latent defect. Where the seller has actual knowledge and deliberately conceals it, the Sevidal line of authorities and Canadian fraud-in-real-estate doctrine generally treat that as a separate exception that contractual disclaimers cannot insulate.

Why this matters: the lawyer's lens

For your real estate lawyer, the practical impact is simple: the only piece of evidence that resolves any radon dispute later is a long-term, lab-analysed test result on letterhead from a C-NRPP-certified Canadian lab. Verbal assurances, screenshots from cheap Amazon monitors, and vendor-promoted "all clear" claims are not admissible-grade evidence in a Sevidal-type dispute. A lab-report PDF in your closing file is.

That document is exactly what a RadonTest.ca kit produces — analysed by Lex Scientific in Guelph, ON, the first independent Canadian laboratory accredited for alpha-track radon analysis by C-NRPP, and ISO/IEC 17025 accredited by CALA.

Province-by-province radon disclosure summary

Verify directly. Provincial regulators update guidance regularly. Always check the current rule in your province through the regulator links above before relying on it for a transaction.

The buyer's playbook

You're about to make a six-figure purchase. Radon is one of the few issues where a $89 test before or after closing can save you a $2,500–$4,500 mitigation bill — and where, in the right circumstances, you can shift that cost to the seller before you sign.

Step 1 — Ask the seller (in writing)

Before you offer, have your buyer's agent ask the listing agent the following questions in an email or text trail you can keep:

1. Has this home ever been tested for radon?
2. If so, was the test performed using a device or professional certified by the Canadian National Radon Proficiency Program (C-NRPP)?
3. If so, may we see a copy of the lab report?
4. Was the test result above 200 Bq/m³?
5. If yes, has any mitigation work been done? May we see proof of installation and a post-mitigation test?

These five questions, in writing, are the BCFSA-recommended buyer's-agent script — they apply equally well in any province. The seller's agent has a professional duty to answer truthfully.

Step 2 — Decide which path fits your closing window

The only test Health Canada and CARST recommend for a remediation decision is a long-term test of 91+ days (Health Canada Guide). Most residential closings don't allow that. You have three practical options, each with trade-offs:

The buyer's-agent default for a residential transaction in 2026 is increasingly some combination of A and B: a short-term screening if the timeline allows it, a holdback in case it doesn't, and a long-term test post-possession either way. If the screening result is "Red" (likely above 200 Bq/m³), the holdback is your safety net; if "Green," the holdback releases to the seller and you've spent very little to know.

Step 3 — Run the long-term test post-possession (always)

Whatever you do during the transaction, run a long-term test once you take possession. CARST's own real-estate guideline is explicit: even after a screening assessment, a long-term test once new owners take possession is required to make a confident remediation decision. (CARST)

A long-term test is what protects you if you ever sell, what triggers a Tarion claim if it applies, and what gives you the answer that actually matters for your family's exposure.

Order your long-term post-possession kit — $89 all-in →

The seller's playbook

For sellers, radon is mostly a risk-management question. Get it wrong and you face the prospect of a buyer rescinding the deal, a post-closing damages claim, or a regulatory complaint against your real estate professional that gets traced back to you. Get it right and a clean radon paper trail becomes a small competitive edge in a slow market.

Should you test before listing?

Pros:

• A clean lab report (below 200 Bq/m³) becomes a marketing asset and removes the issue from buyer negotiations.
• If the result is above 200, you can mitigate before listing — which (per BC and Alberta regulators) removes the "material latent defect" classification, while putting a $3,000–$5,000 mitigation cost behind you that buyers were going to demand anyway. (RECA — Property Considerations)
• A mitigation system is increasingly seen as a positive feature for the home — clean air, future-proofing, and one less negotiation friction.
• Pre-listing testing means you control the timing instead of negotiating against a buyer's clock.

Cons:

• A test takes 91+ days. Sellers often don't plan that far ahead.
• If you do test and the result is high, you have created a disclosure obligation that didn't exist before you tested. In BC and Alberta, regulators have stated that the obligation generally falls away once mitigation is installed and the home is brought below 200 Bq/m³; in other provinces the law on post-mitigation disclosure of prior elevated readings is less developed and your real estate lawyer may recommend continuing voluntary disclosure with documentation.

The pragmatic recommendation, for sellers with planning runway:

Run a long-term radon test as soon as you decide to list within the next 6–12 months. If the result is below 200 Bq/m³, you have a clean lab report to share. If it's above, you have time to mitigate, with the cost behind you, before the home goes on the market.

Order a pre-listing test — $89 all-in →

What you must disclose if you've already tested

The plain-language rule (as expressed by BC and Alberta regulators, and treated similarly under Quebec law and the Sevidal line in Ontario):

A note on the "don't ask, don't tell" trap

There is a temptation for sellers to deliberately not test — on the theory that "what I don't know I don't have to disclose." This was historically common but has become a significantly worse strategy as buyer awareness has grown:

1. Buyers' agents are increasingly trained to ask (CARST Real Estate course, BCFSA buyer's-agent checklist). The "I don't know" answer used to satisfy buyers; today it increasingly triggers a holdback request.
2. The latent-defect doctrine can apply post-closing. If the buyer tests after possession, finds elevated radon, and can establish (under the law of the applicable province) that the seller had actual or, in some circumstances, constructive knowledge of the defect, the seller may face exposure to damages. The threshold and remedy vary by province and by the facts.
3. Mitigation is cheap relative to the deal size. Many sellers find that a $2,500–$4,500 mitigation cost compares favourably to the negotiation friction, price-adjustment requests, or deal-rescission risk that a known-but-unmitigated result can create.

The cleaner play is to test pre-listing, deal with whatever you find, and disclose with documentation.

Order a pre-listing test — $89 →

The realtor's playbook

A 2024 BCFSA notice opens with a single sentence that captures the position every Canadian real estate licensee is in: "You might have heard of radon but have no idea what it is or how it could affect your work as a real estate licensee." (BCFSA Radon Disclosure Reminder). It then lays out, in regulatory plain language, the rule that you cannot afford to miss: known radon above 200 Bq/m³ is a material latent defect, and disclosure must be in writing.

Your professional duty in one paragraph

You are not required to test for your clients, and you are not required to be a radon expert. You are required to: (1) ask sellers and listing agents the right questions, (2) document the answers, (3) advise buyer clients of the importance of testing, (4) pass along known radon information truthfully and in writing, and (5) recommend professional resources where you don't have the expertise yourself. (CARST Real Estate guidance)

Standard scripts (use, document, save to your transaction file)

For buyer clients (verbal + written follow-up):

"Radon is a naturally occurring radioactive gas that can accumulate in Canadian homes. Health Canada estimates roughly 7% of Canadian homes test above the guideline on average, with regional rates exceeding 20% in some provinces. It's the leading cause of lung cancer in non-smokers. I'm advising you to either include a radon screening assessment or a mitigation holdback in your offer, or to plan to run a long-term test once you take possession. Here's a written summary of that recommendation for your records."

For seller clients:

"Has this property ever been tested for radon? If yes, please provide me with any lab reports. If the result was above 200 Bq/m³ and the home hasn't been mitigated, that is a material latent defect we are obligated to disclose to potential buyers in writing. If you've never tested, you have no automatic obligation to test, but I want you aware that a buyer may ask, and I cannot misrepresent the answer."

For listing-agent inquiry (from a buyer's agent):

"On behalf of my client, has this home been tested for radon? If so, by a C-NRPP certified device or professional? May we see a copy of the lab report? If above 200 Bq/m³, has mitigation been performed?"

Resources to bookmark

• BCFSA Radon Precautions Guidelines (gold-standard regulator playbook — applicable thinking in any province)
• CARST For Real Estate (national-association radon resources, scripts, infographics, free certificate course)
• BC Lung Foundation — Real Estate Radon Resources
• CREA / CARST — A Homeowner's Guide to Radon (PDF)
• C-NRPP — Find a Certified Professional

A note for realtors on test-kit choice. When you advise a buyer or seller to test, two practical things matter for your file: (1) the lab is C-NRPP certified, and (2) the lab returns a document admissible in any future dispute. RadonTest.ca ships a $89 all-inclusive kit analysed at Lex Scientific in Guelph, Ontario — the first independent Canadian laboratory accredited for alpha-track analysis by C-NRPP, ISO/IEC 17025 accredited by CALA. Same lab quality as international competitors, with a Canadian paper trail and no US-customs return shipping.

What your real estate lawyer will want to see

For lawyers handling residential closings, radon has moved from "edge case" to "increasingly common condition" in the past three years. Below is general background — the kind of context a buyer or seller might find useful before a closing call with their lawyer. Specific clause language, holdback structures, and dispute strategy are matters for your own real estate counsel — every closing file is different.

Three documents that resolve future disputes

1. A C-NRPP-certified lab report in PDF form — either the seller's pre-listing report, the buyer's screening assessment, or both. Verbal disclosures and email assertions are not admissible in the same way.
2. A clearly drafted holdback clause if any post-closing testing or mitigation is contemplated, specifying threshold (200 Bq/m³), trigger event (a long-term test by a C-NRPP-certified provider), testing window (typically 4–6 months from possession to allow a 91+ day test), release conditions, and dispersal mechanism.
3. A signed acknowledgment of disclosure if elevated radon is known. Standard "as-is" language may not be sufficient on its own where a known latent defect exists — explicit acknowledgment of the specific known defect is the more defensible drafting practice.

Mitigation holdbacks — what to ask your lawyer about

Mitigation holdbacks are widely used in Canadian residential closings to manage radon risk where a long-term test isn't feasible before possession. BCFSA describes them as a "common solution" for this situation, and NBREA explicitly endorses holdback structures tied to a 200 Bq/m³ threshold. (BCFSA, NBREA)

A holdback is, broadly, an agreed amount held in trust at closing by the buyer's lawyer, with release conditions tied to a post-possession long-term radon test. The specific amount, threshold, testing window, dispersal mechanism, and treatment of surplus or shortfall are all negotiated between the parties and drafted by counsel — every file is different. Ask your real estate lawyer about the appropriate structure for your transaction, given the home, the closing timeline, and the risk profile.

For general context on what these clauses do at a conceptual level, see the Mitigation holdbacks: how they actually work section below.

Time-sensitive nature of post-closing claims

Provincial limitation periods apply to any post-closing dispute over an undisclosed defect. These rules vary materially by province (Ontario's Limitations Act, 2002 uses a 2-year basic discoverability period and a 15-year ultimate period; Quebec uses a 3-year prescription under article 2925 of the Code civil du Québec with latent-defect-specific notice rules under articles 1726 and 1739). Limitation periods are fact-sensitive, claim-type-sensitive, and province-specific — confirm the applicable rule in your jurisdiction with your lawyer at the time of the issue, not in advance.

The CARST Real Estate Screening Assessment (4–7 day test) — what it is and isn't

The Canadian Association of Radon Scientists and Technologists (CARST) developed a specific protocol for short-term radon testing during real estate transactions, recognising that the standard 91+ day test is rarely feasible in a closing window. (CARST Real Estate Guidelines, 2018; updated 2020)

Key parameters

• Duration: minimum 4 days; longer is preferred. A test shorter than 48 hours is never acceptable as a radon test under any CARST-approved protocol. (CARST For Real Estate)
• Conducted by: a C-NRPP-certified Measurement Professional, not a do-it-yourself kit.
• Conditions: "closed-house conditions" — windows closed, exterior doors used only for entry/exit, fireplaces off (unless primary heat), HRV/ERV left as found, mitigation systems run as normal.
• Result categories:

How well do short-term tests predict long-term reality?

University of Calgary research cited by CARST gives a candid answer:

"The 5-day tests predicted 90+ day counterparts 80% of the time (r² = 0.805) … Short-term test precision displayed progressively decreasing [accuracy] the further into warmer temperature months that short-term tests took place."

In plain terms: a winter 5-day screening assessment showed strong correlation with long-term annual averages; a summer 5-day screening assessment showed essentially no correlation (the same study reported r² = 0.011 for summer 5-day vs. winter 90+ day). The "80%" figure is a high-level summary metric; r² values are the underlying statistical correlation. Either way, the practical point is the same. (CARST For Real Estate — University of Calgary research)

The two practical conclusions:

1. A screening assessment in heating season (October–April) is informative. Outside heating season, treat it as more like a coin flip.
2. Always follow up with a long-term test post-possession. This is non-negotiable per CARST and Health Canada — a screening assessment is screening, not diagnosis.

Industry note

Industry research is moving toward shorter validated test methods that may further compress closing-window testing timelines in coming years. We will update this article as new C-NRPP-recognised protocols are published.

Mitigation holdbacks: how they actually work (in plain language)

A mitigation holdback is the most common tool Canadian buyers and sellers use to manage radon risk when a 91+ day test isn't feasible before possession.

The general idea. Buyer and seller agree, as a term of the offer, that an amount of money (often referenced in the $3,000–$5,000 range, reflecting typical Canadian mitigation costs) will be held in trust by the buyer's lawyer at closing. The buyer commits to running a long-term radon test (91+ days) within a defined window post-possession. If the test result is below the Health Canada guideline of 200 Bq/m³, the funds release to the seller. If it's above, the funds are applied to mitigation by a certified mitigator.

Why regulators support this approach. BCFSA describes holdbacks as a "common solution" and recommends them where pre-closing testing isn't feasible. (BCFSA Radon Precautions Guidelines) NBREA explicitly endorses holdback structures tied to a 200 Bq/m³ threshold. (NBREA radon guidance)

What gets negotiated. The dollar amount, the trigger threshold (200 Bq/m³ is the typical Health Canada-aligned standard, though some buyers reference the WHO's 100 Bq/m³), the testing window (4–6 months from possession is common to comfortably accommodate a 91+ day test), and how surplus or shortfall is handled.

Important — these are illustrative descriptions of what holdbacks do, not legal drafting advice. The specific clause language for your transaction is the job of your real estate lawyer, who will tailor it to the property, the parties, and the closing timeline.

For your part as a buyer, the document the holdback ultimately depends on is the long-term lab-analyzed test result. A RadonTest.ca kit — C-NRPP-listed device, analyzed by a C-NRPP-certified Canadian lab, written lab report PDF — is purpose-built for that role, with no US-customs return shipping that could blow past your release window.

Special situations

Buying a new build in Ontario — Tarion radon coverage

If you're buying a new build in Ontario whose Agreement of Purchase and Sale was signed on or after February 1, 2021, and the home is within its 7-year warranty window, Tarion's statutory new-home warranty covers up to $50,000 of radon mitigation if a qualifying long-term test shows levels above 200 Bq/m³. (Tarion radon coverage)

The qualifying test, per Tarion's published requirements, is a long-term (minimum 3-month) test in the basement, using a device or testing professional certified by the Canadian National Radon Proficiency Program (C-NRPP), with lab analysis. (Tarion radon coverage) A $89 RadonTest.ca kit — C-NRPP listed device, analysed by a C-NRPP certified Canadian lab — meets these requirements; see our full Tarion warranty claim guide for the step-by-step filing process.

Buying a resale within Tarion's 7-year window

Tarion's radon warranty travels with the home, not the original buyer. If you're purchasing a resale Ontario home that's still within the 7-year window from the original date of possession, you inherit the remaining coverage. (Tarion FAQs)

To complete the transfer, contact Tarion at 1-877-9-TARION right after possession with your Agreement of Purchase and Sale and transfer deed. They will register you as the new owner and you can access MyHome to file claims. Test post-possession with a long-term kit so you have the lab report you need if you ever do file. (Tarion Purchaser FAQs) See our Tarion claim guide for the resale transfer process in detail.

Buying a home with an existing mitigation system

A home with a properly installed C-NRPP-certified mitigation system is, in most regulators' view, a positive selling point — not a defect. Ask for:

• The original pre-mitigation lab report (if available)
• The mitigator's installation documentation, including warranty
• A post-mitigation test confirming levels below 200 Bq/m³
• Ideally an independent post-mitigation test, not just the mitigator's own commissioning test (see post-mitigation independence)

Then run your own long-term test post-possession. Mitigation systems use continuous-duty fans that have a typical 8–12 year lifespan, and system effectiveness can drift over time.

Buying a rental / income property

Radon is a recognized indoor air contaminant under Health Canada's published guidance, and CARST publishes specific landlord and tenant guidance on testing and remediation. Provincial tenancy and workplace-health regimes treat indoor air quality differently, and tenant expectations are increasingly informed by health-authority messaging on radon. Once a tenant raises radon as a concern, declining to test creates a paper trail many landlords would rather not have.

If you're buying with the intent to rent, test pre-leasing. A clean lab report below 200 Bq/m³ closes the question; a result above gives you the chance to mitigate before tenants move in.

After closing: the long-term follow-up test (and the independence rule)

Whatever happened in the transaction, run a long-term (91+ day) radon test once you take possession. This is the test that gives you the answer that matters for your family's exposure, the answer that triggers a Tarion claim if it applies, and the answer that protects you when you eventually sell. (Health Canada Guide)

If the test comes back above 200 Bq/m³ and you mitigate, run an independent post-mitigation test from a separate provider, not the mitigator's own commissioning test. This is a basic conflict-of-interest issue: a mitigator who installs a $3,500 system and then certifies their own work is the same problem as a contractor who builds a deck and then signs off on its safety inspection. The result you keep on file should come from a provider with no financial interest in the system having worked.

RadonTest.ca does not install mitigation systems — that independence is deliberate and is exactly what you want for a post-mitigation verification document.

Frequently asked questions

Do I have to test for radon before selling my home in Canada?

No. You have no automatic obligation to test for radon before listing. However, if you have ever tested and the result was above 200 Bq/m³ and you have not mitigated, BC and Alberta regulators (and the latent-defect doctrine more broadly) treat that as a material latent defect that must be disclosed in writing. If you've never tested, you can rely on caveat emptor for what you don't know — but you must answer questions truthfully. (BCFSA)

Do I have to disclose radon when selling in Canada?

If you have actual knowledge of elevated radon (above 200 Bq/m³) in the home and have not mitigated, yes — across most provinces this is treated as a "material latent defect" requiring disclosure. BC and Alberta regulators require written disclosure expressly; in other provinces the obligation flows from the latent-defect doctrine through case law and provincial real-estate regulator guidance. If you have mitigated and a post-mitigation test confirms levels below 200 Bq/m³, the express written-disclosure rule generally falls away in BC and Alberta, but you must still answer questions truthfully and disclosing the mitigation history voluntarily is best practice everywhere.

Do you have to disclose radon when selling a house in Ontario?

Ontario does not have an express provincial regulator rule requiring written radon disclosure on the level of BC or Alberta, but the latent-defect doctrine (the Sevidal line of cases) applies, and OREA's Form 220 (SPIS) flags environmental concerns. If you have actual knowledge of elevated radon and have not mitigated, the more defensible practice — confirmed by Ontario real estate counsel — is to disclose with documentation.

Should I include a radon clause in my Ontario real estate offer?

Yes, if you're a buyer and the home has not been long-term tested. The two standard mechanisms are a radon contingency in the conditional-offer period (using a CARST short-term Real Estate Screening Assessment by a C-NRPP-certified professional) and a mitigation holdback at closing. See the Buyer's Playbook above. Talk to your real estate lawyer about specific clause language for your transaction.

Does a home inspection in Canada include radon testing?

Almost never. A standard pre-purchase home inspection does not test for radon. If you want a radon test as part of a real-estate transaction, you need to hire a C-NRPP-certified Measurement Professional separately, or arrange a long-term test post-possession (the RadonTest.ca $89 kit is purpose-built for this).

Which radon test "counts" in a Canadian real estate transaction?

Two tests count, for two different purposes. A CARST short-term Real Estate Screening Assessment (4–7 days, by a C-NRPP-certified professional, under closed-house conditions) counts as a screening signal during a conditional-offer or subject-removal window. A long-term (91+ day) alpha-track test, lab-analysed by a C-NRPP-certified laboratory, counts as the diagnostic result that supports a mitigation decision, a Tarion warranty claim, or a future disclosure. The long-term test is the document a real estate lawyer or Tarion adjudicator will ultimately want — see the Buyer's Playbook and What your real estate lawyer will want to see sections above for how each fits into a transaction.

Can I include a radon condition in my offer to purchase?

Yes. Two common structures: a conditional offer with a CARST short-term Real Estate Screening Assessment (4–7 days, by a C-NRPP-certified professional) during the subject-removal period; or a mitigation holdback clause that reserves funds in trust at closing pending a post-possession long-term test. Both are recognised by provincial regulators. (BCFSA, NBREA) Talk to your real estate lawyer about the specific clause language.

How much should the holdback be?

Mitigation typically costs $2,500–$4,500 in Canada, occasionally up to $11,000 for complex homes. Holdbacks of $3,000–$5,000 are common; $7,500 for older or more complex homes is not unusual.

Can a home inspector test for radon during a typical inspection?

No. A standard home inspection does not include radon testing. Even the CARST-recognised short-term Real Estate Screening Assessment requires a separate visit by a C-NRPP-certified Measurement Professional, a minimum 4-day duration, and "closed-house" conditions during the test period. Anything advertised as a "1-hour radon test" is not a CARST-recognised test and should be disregarded.

What about the cheap "smart" radon detectors on Amazon?

Health Canada has issued multiple recalls and safety advisories on consumer radon detectors sold on Amazon.ca and similar platforms in recent years, citing inaccurate readings. Always check the current Health Canada Recalls database and the C-NRPP Consumer-Grade Electronic Radon Monitors list before buying any digital monitor. For a real-estate transaction, the more defensible choice is a long-term alpha-track kit lab-analysed by a C-NRPP-certified Canadian lab — the RadonTest.ca $89 kit is built for exactly this use case.

Does the Tarion warranty in Ontario apply to me as a resale buyer?

Yes, if the home is within its 7-year window from the original date of possession. The warranty travels with the home, not the original buyer. Contact Tarion at 1-877-9-TARION after possession to register as the subsequent owner. (Tarion FAQs) See our Tarion claim guide.

Can I rescind a deal after closing if I find radon?

Whether any post-closing remedy (rescission, damages, or other) is available depends on many fact-specific issues — including what the seller actually knew, what was disclosed, the language of the purchase agreement, the applicable provincial limitation period, and the strength of any contractual disclaimer. This is a question for a real estate lawyer in your province — we cannot give you an answer to it here. The general legal context is described in the legal framework and What your real estate lawyer will want to see sections above.

Are realtors and real estate brokerages liable if they don't disclose known radon?

Provincial real estate regulators have made it explicit that licensees must disclose known material latent defects in writing, and that failure to do so can give rise to professional discipline (which may include fines, conditions on licence, or licence action depending on the regulator and the facts). (BCFSA) Civil liability for damages — separate from regulatory discipline — is also a possibility under common-law negligence and the latent-defect doctrine in the relevant province; outcomes depend on the specific facts and would be assessed by a court.

What test does Tarion accept for a radon warranty claim?

A long-term test of at least 3 months (and up to 12 months), using a device or testing professional certified by the Canadian National Radon Proficiency Program, in the basement (not a crawl space), lab-analyzed by a C-NRPP-certified lab. (Tarion radon coverage) The RadonTest.ca $89 kit meets all three requirements.

How often should I retest after I buy?

Health Canada recommends every 5 years, or after any significant change to the home (new HVAC, basement renovation, foundation work). Sooner if you mitigated and want to confirm sustained reduction, or if the home enters a different use (e.g., a basement bedroom is added).

Will my home insurance cover radon mitigation?

Generally no. Standard Canadian home insurance policies do not cover radon mitigation costs, because radon is a naturally occurring condition rather than a sudden insured peril. The exceptions are warranty programs (Tarion in Ontario for new builds within their 7-year window) and provincial financing or tax credit programs (e.g., Manitoba Hydro's Energy Finance Plan; Saskatchewan's renovation tax credit). (Health Canada — Provincial Policies) Confirm with your insurer.

For realtors and lawyers — bookmark this guide

If you handle Canadian residential transactions, this article is built to be re-used: share the URL with clients, link from your brokerage or firm wiki, or print the relevant section as part of your client onboarding pack. Specific workflow callouts:

• Buyer's agents: the Buyer's Playbook section is a complete pre-offer script. The five-question seller inquiry can be copied into your client email templates.
• Listing agents: the Seller's Playbook explains why pre-listing testing is the modern best practice and what the legal exposure looks like if it isn't done.
• Real estate lawyers: the What your real estate lawyer will want to see section gives clients useful background context before a closing call. Specific clause language is your call.
• Mortgage brokers and home inspectors: the legal framework and province-by-province summary are useful client-conversation references.

If you'd like a printable PDF version of any of these sections for your client onboarding pack, contact us.

Order your kit

For buyers, sellers, realtors, and lawyers — when the question is "which test produces a document that holds up in a transaction or a dispute," the answer is the same:

RadonTest.ca — $89, all-in. Long-term 91-day alpha-track kit. C-NRPP-listed device. Analysed at Lex Scientific in Guelph, Ontario — Canadian lab, C-NRPP listed, ISO/IEC 17025 accredited by CALA. Tracked outbound, prepaid tracked Canada Post return label included. No US-customs return shipping that could blow past your closing-clause deadlines. Written lab report PDF — the document a real estate lawyer, a Tarion adjudicator, or a future buyer will accept.

Order — $89 →

Important disclaimers

Not legal advice. This article is general information about Canadian real estate radon disclosure as of May 2026. It is not legal, professional, or warranty advice and is not a substitute for advice from a qualified real estate lawyer in your province. Laws, regulations, regulator guidance, and standard form language change. Always verify the current rule in your jurisdiction and consult a qualified professional before relying on any of this in a transaction or claim.

Province-specific variation. Real estate disclosure obligations vary materially across Canadian provinces and territories. Statements about specific provinces are summaries based on publicly available regulator and association guidance and are not a substitute for province-specific legal review.

Case law and limitation periods. Sevidal v. Chopra and similar decisions are cited for general illustrative purposes. Outcomes in any specific dispute depend on the facts, the language of the agreement, and the applicable provincial limitation periods (which vary). This article does not predict or guarantee any outcome in litigation.

Holdback and conditional-offer clauses. Sample clause structures in this article are illustrative only and are not a substitute for clause language drafted by your real estate lawyer or your brokerage's standard forms.

Pricing and product information. Mitigation cost ranges, test pricing, and product details reflect publicly available information as of May 2026 and are subject to change. Verify current pricing and product specifications with the relevant providers before relying on them.

Affiliations. RadonTest.ca is an independent Canadian radon test kit provider. We are not affiliated with Tarion, the Real Estate Council of Ontario, the Ontario Real Estate Association, the Canadian Real Estate Association, the BC Financial Services Authority, the British Columbia Real Estate Association, the Real Estate Council of Alberta, the Organisme d'autoréglementation du courtage immobilier du Québec (OACIQ), the New Brunswick Real Estate Association, the Canadian Association of Radon Scientists and Technologists (CARST), Health Canada, or any other regulator, professional body, or vendor named in this article. References are for descriptive and verification purposes only. Tarion's rules, BCFSA's rules, and any other regulator's published guidance govern any specific transaction or dispute.

Lex Scientific partnership. RadonTest.ca's laboratory analysis is performed by Lex Scientific Inc. of Guelph, Ontario, an independent C-NRPP-certified, ISO/IEC 17025 (by CALA) accredited Canadian laboratory. We are not Lex Scientific; we contract with them for analysis services.

No warranty as to completeness. RadonTest.ca makes no warranty as to the completeness or accuracy of the information herein and accepts no liability for decisions made in reliance on this article. Readers should independently verify any information that bears on a transaction, claim, or construction decision before acting.

Sources

Health Canada / federal

• Guide for Radon Measurements in Residential Dwellings
• Testing your home for radon
• Radon action guide for provinces and territories: Policies for specific locations
• Radon Reduction Guide for Canadians

National associations

• CARST — Radon for Real Estate Agents
• CARST — Things to Consider When Buying a Home
• CARST — Landlords and Tenants
• CARST — Guideline for Conducting a Radon Screening Assessment as Part of a Real Estate Transaction (2020)
• C-NRPP — Find a Certified Professional / Lab
• C-NRPP — Consumer-Grade Electronic Radon Monitors
• CREA / CARST — A Homeowner's Guide to Radon (PDF)
• Take Action on Radon — Order a Radon Test Kit (provincial directory)

British Columbia

• BCFSA — Radon Precautions Guidelines
• BCFSA — Radon Disclosure Reminder (Feb 2024)
• BCFSA — Consumer Guide to Radon
• BCREA — Property Disclosure Statement Online Course
• BC Lung Foundation — Radon and Real Estate Resources

Alberta

• RECA — Property Considerations
• RECA — Radon Information Bulletin (PDF)
• RECA — Material Latent Defects Bulletin (PDF)
• RECA — Raising Your Client's Radon Awareness (May 2025)

Ontario

• Tarion — How your new home warranty protects you against the dangers of radon gas
• Tarion — Purchaser & Homeowner FAQs (warranty transfer)
• Larson Lawyers — SPIS and Real Estate Disclosures in Ontario
• Aaron & Aaron — How the courts have shown it's "buyer beware" when purchasing property

Quebec

• OACIQ — Radon Professional Practices Guide
• OACIQ — Radon infiltration in a building (consumer page)
• OACIQ — Declarations by the seller of the immovable (PDF)

Atlantic Canada

• NBREA — Radon: What you need to know

Case law and commentary

• CanLII — Caveat Emptor and the Sale of Land: The Erosion of a Doctrine
• Sullivan Mahoney — The Law of Latent Defect

Related RadonTest.ca articles

• How to Claim the Tarion Radon Warranty in Ontario (Up to $50,000 Coverage)
• Canadian Building Codes and Radon: What Ontario Homeowners Need to Know (2026 Guide)
• Best Radon Test Kit in Canada (2026): An All-Canadian Alternative to AccuStar & Radonova, Compared
• Long-Term Radon Test vs Continuous Digital Monitor (Canada, 2026)