Most homebuyers never think about the air they will be breathing in the home they are about to buy. Radon does not show up during a walk-through. It has no smell, no colour, and no taste. But radon is the second leading cause of lung cancer in Canada after smoking, and a significant portion of homes across Alberta test above the level Health Canada considers safe.

If a radon test on a home you are buying comes back high, the question becomes what to do about it. The answer is radon mitigation, a permanent system installed in the home that pulls radon gas out from under the foundation and vents it safely outside before it can build up inside.

This guide explains what radon mitigation actually is, how the system works, why it matters for the home you are about to buy, and what to look for during your inspection. By the end of this post you should be able to read a radon report, understand whether mitigation is needed, and recognize what a properly installed system looks like.

Watch the Inspection

Key Issues Found

• A Canadian home tested above the Health Canada radon action level
• Radon was entering through the foundation, plumbing penetrations, and the sump pit
• The home required an active soil depressurization (ASD) mitigation system
• Pre-installation building diagnostics were needed to design the system correctly
• The vent stack needed to discharge above the roofline to prevent re-entry of radon gas

What Is Radon?

Radon is a naturally occurring radioactive gas produced by the breakdown of uranium in soil and rock. It is colourless, odourless, and tasteless, which means there is no way to detect it without specific testing equipment.

Outdoors, radon disperses harmlessly. The problem starts when radon seeps into a home through the foundation and gets trapped indoors. Indoor radon concentrations can climb to levels that significantly increase the risk of lung cancer over years of exposure.

Health Canada has set the radon action level at 200 becquerels per cubic metre (Bq/m³). If a home tests at or above 200 Bq/m³, Health Canada recommends taking action to reduce it. Many homes across Alberta, Saskatchewan, and other parts of Canada test above this level.

How Does Radon Get Into a Home?

Radon enters wherever the building has direct or indirect contact with the soil. The most common entry points are:

• Cracks in the concrete foundation slab or basement walls
• Gaps around plumbing lines that pass through the foundation
• Open or unsealed sump pits
• Unsealed floor drains
• Cold joints between the slab and the foundation walls
• Crawl spaces with bare earth floors

Any home, new or old, can have a radon problem. New construction often shows higher radon levels than older homes because newer homes are sealed tighter. Once radon gets in, it stays in.

What Is Radon Mitigation?

Radon mitigation is the process of installing a permanent system in a home to reduce indoor radon levels below the Health Canada guideline of 200 Bq/m³. The most common and effective method used across Canada is called active soil depressurization, or ASD.

How an Active Soil Depressurization System Works

An ASD system removes radon from underneath the home before it can enter the living space. The basic steps are:

1. A small hole is drilled through the concrete slab of the basement or lowest level.
2. A sealed pipe is run from that hole, through the home, and vented outside above the roofline.
3. An inline fan is installed on the pipe.
4. The fan creates negative pressure beneath the slab, pulling radon gas out of the gravel layer and venting it safely outside, away from windows and doors.

A well-designed ASD system typically reduces radon levels by 80 to 99 percent. Many systems bring the home down well below 100 Bq/m³.

The fan runs continuously but uses very little electricity, typically less than the cost of a standard light bulb running 24 hours a day.

Why a Pre-Installation Diagnostic Matters

Not every home benefits from the same mitigation design. Before any drilling happens, a certified contractor should perform a building diagnostic, sometimes called a communication test. This confirms:

• The slab and sub-slab gravel can be properly depressurized
• The correct location for the suction point
• Whether more than one suction point is required
• The size of the fan needed

Skipping this step is one of the most common reasons a system fails to lower radon levels. A mitigation system designed without diagnostics is a guess. Homebuyers should not pay for guesses.

What This Means for Homebuyers

If you are buying a home and a radon test comes back at or above 200 Bq/m³, mitigation is the answer. A few things to keep in mind:

A properly installed ASD system reliably reduces radon to safe levels in almost every home. Mitigation is typically a one-time cost. Once installed, the system runs quietly in the background for the life of the home.

The cost of mitigation in Canada varies based on the home's foundation type, size, and complexity. Always get a written quote from a certified contractor. You can ask the seller to install mitigation as a condition of the sale, or negotiate a price reduction so you can install it after closing.

Radon is one of several invisible hazards Canadian buyers should test for. Older homes can also hide problems like vermiculite insulation in the attic, which carries its own asbestos-related risks. Both are reasons to never skip the inspection.

Always use a C-NRPP certified contractor. C-NRPP stands for the Canadian National Radon Proficiency Program, and it is the recognized standard for radon professionals in Canada.

What to Look For

Use this checklist when walking through a home you are considering:

• Is the home in an area known for elevated radon? Most of Alberta, including Medicine Hat and Brooks, is considered high risk. You can check your region on the Take Action on Radon website.
• Is the basement finished? Finished basements can hide foundation cracks and unsealed sump pits.
• Is there a visible sump pit? If so, is it sealed and capped?
• Is there a radon mitigation system already installed? Look for a sealed vertical PVC pipe running from the basement up through the home and out the roof, with an inline fan.
• If a system is installed, does it vent above the roofline, away from windows and doors?
• Ask the seller or your inspector for a recent radon test result. If there is no test, plan to do one after closing.

Frequently Asked Questions

How do I know if my house has high radon?

The only way to know is to test. Use a certified long-term radon test kit (90 days is the recommended duration) or hire a C-NRPP certified professional to test the home. Short-term tests can flag a problem but should be confirmed with a long-term result.

How much does radon mitigation cost in Canada?

Costs vary based on the home's size, foundation type, and layout. As a general range, a typical residential mitigation system in Canada is a one-time installation cost in the low thousands of dollars. Always get a written quote from a C-NRPP certified contractor.

Can I install a radon mitigation system myself?

You can, but it is not recommended. A system designed without proper building diagnostics often fails to reduce levels enough, which means money spent on a system that does not work. A certified contractor designs the system based on how air actually moves under your specific home.

Does radon mitigation increase my home's value?

A properly installed and documented radon mitigation system is generally seen as a positive feature in a Canadian home, especially in high-risk regions. It is proof that the home has been tested and the issue has been actively managed.

How long does a radon mitigation system last?

The piping and ductwork last for decades. The inline fan typically needs replacement every 8 to 12 years. The system should be tested periodically to confirm it is still bringing radon levels down to a safe range.

Can radon levels change after the system is installed?

Yes. Radon levels in a home naturally fluctuate based on weather, season, and how the home is being used. A well-designed mitigation system keeps levels well below the guideline even when conditions push radon higher. Retest every two years and after any significant renovation.

Is radon a bigger problem in Alberta?

Yes. Many parts of Alberta, including Medicine Hat, Brooks, and surrounding communities, are considered high radon risk areas. The local geology produces uranium, and tightly built homes hold the gas inside once it enters. Every Alberta home should be tested.

What is the difference between radon testing and radon mitigation?

Radon testing measures the level of radon in a home. Radon mitigation is the system installed to reduce it. Testing comes first. If the result is at or above 200 Bq/m³, mitigation is the next step.

Final Thoughts

Radon is a real risk in Canadian homes, and it is one of the few risks a standard home inspection alone cannot rule out. The gas requires specific testing, and if levels are high, it requires a properly designed mitigation system to bring those levels safely down.

If you are buying a home in Medicine Hat, Brooks, or anywhere in southern Alberta, a radon test is one of the most valuable inspections you can add to your due diligence. And if the home needs mitigation, work with a C-NRPP certified contractor who runs proper building diagnostics before installing the system.

I work for you, not the deal. When I flag radon during an inspection, I am flagging it because it matters for your family, not because it makes the transaction easier for someone else. If you are curious about what other inspectors miss during a standard walk-through, read Home Inspection Today: Learn What Others Miss.

Book your inspection today.