Introduction:

Radon is an invisible, odorless, and tasteless radioactive gas that seeps into homes through the ground. It forms naturally when uranium in soil and rock breaks down — and it can accumulate indoors without any visible signs.

While you can’t see or smell radon, its impact is deadly serious. According to Health Canada, radon exposure is responsible for over 3,000 lung cancer deaths every year, making it the second leading cause of lung cancer after smoking.

The only way to know if your home is safe is through radon testing. But to get accurate, trustworthy results, how you prepare for the test, maintain the right conditions during testing, and respond afterward are just as important as the test itself.

Whether you’re doing a DIY radon test kit or hiring a professional radon testing service, this step-by-step guide will help you know exactly what to do before, during, and after your radon test — so you can protect your family and home like a pro.

1. Understanding the Basics: Why Radon Testing Matters

Before you begin testing, it helps to understand why this process is so important.

Radon gas moves up through soil and rock and can enter your home through:

• Cracks in the foundation, floors, and walls
• Gaps around pipes, drains, and electrical conduits
• Crawl spaces or unsealed joints
• Sump pumps and floor drains

Once inside, radon can build up — especially in basements, crawl spaces, or lower levels. The more sealed and energy-efficient a home is, the more likely radon levels can become elevated.

Because radon levels fluctuate daily and seasonally, testing under the right conditions ensures your results reflect your home’s true exposure risk.

2. What to Do Before a Radon Test

Preparation is everything. Before you begin your radon test — whether professional or DIY — there are several steps you should take to ensure accurate, reliable results.

Step 1: Decide Between a Professional Test or DIY Kit

There are two main ways to test for radon:

1. Professional Radon Test

• Conducted by a certified radon measurement specialist
• Uses calibrated Continuous Radon Monitors (CRMs)
• Measures radon hourly and tracks humidity, pressure, and temperature
• Provides detailed reports and tamper-proof results

Best for: Real estate transactions, long-term verification, or high-accuracy testing.

2. DIY Radon Test Kit

• Affordable, simple, and available at hardware stores or online
• Typically uses charcoal canisters or alpha track detectors
• Requires the homeowner to follow setup and mailing instructions

Best for: Preliminary testing or ongoing homeowner awareness.

Pro Tip:

For first-time testers, start with a short-term test (2–7 days). If results are near or above the safety threshold, follow up with a long-term test (90+ days).

Step 2: Choose the Right Time of Year

Radon levels fluctuate throughout the year.

They are typically highest in winter when windows and doors remain closed, creating stronger indoor air pressure differences.

Best testing times:

• Late fall through early spring
• During heating season (October–April)

Avoid testing during:

• Strong storms or high winds
• Home renovations or construction (they affect airflow)

Testing during winter months ensures your readings reflect worst-case conditions, which helps you make informed mitigation decisions.

Step 3: Select the Best Testing Location

Radon testing should be done in the lowest livable area of your home — the area where people spend the most time.

Ideal locations:

• Basement family room
• Finished basement bedroom
• Ground-level living space

Avoid testing in:

• Kitchens, bathrooms, or laundry rooms (moisture and ventilation distort results)
• Near open windows, air vents, or heating ducts
• Direct sunlight or near exterior walls

Placement Guidelines:

• 2 to 6 feet above the floor
• At least 1 foot away from exterior walls
• Away from drafts, heat sources, or electronic devices
• On a stable surface where it won’t be disturbed

If your home has multiple levels, test each floor over time or use multiple detectors for the most accurate assessment.

Step 4: Prepare the Home — Establish Closed-Building Conditions

To ensure accurate radon readings, your home must be under closed-building conditions before and during the test.

What this means:

• Keep all exterior doors and windows closed for at least 12 hours before starting the test.
• Operate heating and cooling systems normally, but don’t introduce fresh outdoor air.
• Avoid running fans or ventilation systems that draw in outside air (like HRVs, attic fans, or range hoods).
• Minimize fireplace and wood stove use.

The goal is to simulate typical indoor air conditions that allow radon to accumulate naturally.

Step 5: Read and Follow All Instructions Carefully

If you’re using a DIY radon kit, read the manufacturer’s instructions closely before opening the package. Most kits include:

• A test device
• Instruction sheet
• Data card (for location, date, and time)
• Prepaid mailer or return envelope

Be sure to:

• Record the start date and time when you begin
• Note the testing location (e.g., “finished basement, north wall”)
• Avoid moving the kit during the testing period

Common Mistake to Avoid:

Placing the device near vents or forgetting to mail it promptly after the test — this can invalidate your results.

3. What to Do During a Radon Test

Once the test begins, your job is to maintain consistent home conditions and avoid disrupting the device.

Here’s how to ensure your radon test runs smoothly and produces valid data.

Step 1: Maintain Closed Conditions

Continue keeping all windows and exterior doors closed throughout the entire testing period.

You can still enter and exit the home, but minimize it as much as possible.

Do:

• Use your heating or cooling system as usual.
• Live in your home normally (sleep, cook, etc.).

Don’t:

• Open windows or doors for extended periods.
• Run fans that vent air outdoors.
• Leave the test unattended in a drafty or humid area.

Remember: even small changes in airflow can drastically affect the reading.

Step 2: Avoid Moving or Touching the Device

Whether it’s a professional monitor or a DIY test kit, the detector should remain untouched and undisturbed throughout the test duration.

• Don’t move it for cleaning or vacuuming.
• Keep pets and children away from it.
• Avoid bumping or covering it with objects.

Pro Tip:

Some professional monitors include tamper sensors that detect movement, light exposure, or pressure changes — which helps ensure the test is valid.

Step 3: Record Environmental Conditions (Optional but Helpful)

If you’re serious about accuracy, note down:

• Indoor temperature
• Weather conditions (e.g., heavy rain, snow, wind)
• HVAC usage

These details help professionals interpret variations in radon levels later.

Continuous radon monitors automatically track these variables, but manual kits benefit from basic notes.

Step 4: Let the Test Run the Full Duration

Don’t end the test early, even if you’re eager to know the results.

Most short-term radon tests require 48 to 96 hours for a valid average reading.

If you stop too soon, you’ll only capture part of the daily radon cycle — which can fluctuate dramatically based on temperature, air pressure, and occupancy.

Let the test run to completion as instructed for the best accuracy.

Step 5: Keep Normal Living Habits

You don’t need to leave your home or change your lifestyle during the test. In fact, living normally helps the test reflect real-world conditions.

Just avoid doing anything that increases ventilation dramatically — such as:

• Opening basement windows
• Using exhaust fans for long periods
• Drying laundry indoors with open windows

Your goal is to simulate everyday indoor air conditions as much as possible.

4. What to Do After a Radon Test

Once the testing period ends, the next phase is equally important — handling and interpreting your results correctly.

Step 1: End the Test Properly

When the test duration is over:

• Record the end date and time.
• Seal the test device as directed (for charcoal kits, close the lid or seal the bag).
• If required, fill out the included data card with your name, address, and details.

If using a digital monitor, save or record your data before resetting the device.

Step 2: Send the Test to the Lab Promptly

Mail your test device to the laboratory immediately.

Most radon kits must be received by the lab within 24–48 hours after the test ends to ensure validity.

Delays in mailing can cause inaccuracies, as the sample may continue absorbing or losing radon before analysis.

Professional testers handle this step automatically since their monitors store digital data securely.

Step 3: Review Your Results

Results typically arrive within a few days (DIY kits) or immediately for digital monitors.

Radon levels are reported as:

• Becquerels per cubic meter (Bq/m³) in Canada
• Picocuries per liter (pCi/L) in the United States

Interpreting Results:

CountrySafe LevelAction LevelRecommendation

Canada Below 200 Bq/m³ 200+ Bq/m³ Mitigate within 2 years

USA Below 4.0 pCi/L 4.0+ pCi/L Mitigate as soon as possible

WHO Below 100 Bq/m³ 100+ Bq/m³ Ideal long-term goal

If your results are below 200 Bq/m³ (or 4.0 pCi/L), your home is considered safe.

If levels are higher, don’t panic — radon can be fixed effectively and affordably.

Step 4: Take Action if Levels Are High

If your radon readings exceed safety guidelines, contact a certified radon mitigation professional for inspection.

Professional mitigation methods include:

1. Sub-Slab Depressurization (SSD):
2. A vent pipe and fan draw radon gas from beneath the foundation and vent it safely outdoors.
3. Crawl Space Sealing:
4. Encapsulating crawl spaces with plastic barriers.
5. Sump Lid Sealing:
6. Covering sump pits to block radon entry.
7. Increased Ventilation:
8. Installing HRV systems to dilute indoor radon.

After installation, a follow-up test confirms the system’s success.

Step 5: Retest Periodically

Even after a successful mitigation, retesting every 2–3 years is essential.

Why?

• Soil conditions change.
• Cracks can reappear.
• Fans or systems can fail.

You should also retest after:

• Major home renovations
• Basement finishing
• HVAC system replacement

Consistent testing ensures your home stays safe long-term.

5. Common Mistakes Homeowners Make During Radon Testing

Even the best intentions can go wrong if simple steps are missed. Here are the most common testing mistakes and how to avoid them.

1. Not Maintaining Closed-Building Conditions

Opening windows during the test drastically lowers radon levels, producing false-safe results.

2. Wrong Placement

Placing the kit near vents, windows, or walls skews results. Always follow placement guidelines carefully.

3. Short Testing Period

Ending the test early or mailing late invalidates your data. Respect the recommended duration.

4. Ignoring Seasonal Variations

Testing in summer can underestimate radon. Always test in the colder season or do a long-term test across multiple months.

5. Misinterpreting Results

Some homeowners see borderline results and assume safety. Always follow up with a long-term test or professional retest to confirm.

6. Why Professional Radon Testing Is Worth It

If you’re unsure about doing it yourself, professional testing offers peace of mind and superior accuracy.

Benefits:

• Certified calibrated equipment (Continuous Radon Monitors)
• Hourly readings with environmental tracking
• Tamper-proof data
• Interpreted reports with actionable recommendations
• Recognized by real estate, insurance, and health agencies

Professional testing is especially important if:

• You’re buying or selling a home
• You’ve had previous high radon results
• You live in a known high-radon area (like Ottawa, Winnipeg, or Calgary)

Cost Range (Canada): $250–$450 for professional testing

DIY Kits: $40–$80 (plus mailing fees)

While DIY testing is good for screening, professional tests are the gold standard for legal and mitigation decisions.

7. Frequently Asked Questions About Radon Testing

Q1. How long should a radon test run?

Short-term tests last 2–7 days. Long-term tests last 90+ days for more accurate averages.

Q2. Can weather affect radon test accuracy?

Yes. Wind, rain, and barometric pressure can alter indoor radon levels. That’s why long-term tests are more reliable.

Q3. Should I test for radon in new homes?

Absolutely. New homes are often sealed tighter, which can trap more radon gas.

Q4. How often should I test for radon?

Every 2–3 years, or after any major renovation or mitigation work.

Q5. Can I use an air purifier to remove radon?

No. Air purifiers don’t remove radon gas — only proper mitigation systems can.

Q6. How can I find a certified radon professional near me?

In Canada, visit C-NRPP.ca (Canadian National Radon Proficiency Program).

In the U.S., check NRPP.info (National Radon Proficiency Program).

8. Radon Testing in Ottawa: A Real-World Example

Ottawa is one of Canada’s most radon-prone cities. The combination of its uranium-rich soil and cold winters means radon levels are often elevated.

Health Canada studies show that 1 in 3 homes in Ottawa exceed safe radon limits.

Local experts recommend:

• Testing every 2 years
• Using certified C-NRPP professionals
• Prioritizing winter testing for accuracy

If you live in Ottawa, search “radon testing Ottawa” or “radon mitigation Ottawa” to find certified local specialists offering free consultations and professional testing.

9. Summary: The Complete Timeline for a Radon Test

Here’s a quick recap of what to do before, during, and after your test:

Before the Test

✅ Choose between DIY or professional testing

✅ Select the lowest livable area for placement

✅ Close all windows and doors 12 hours before testing

✅ Record start date/time and follow instructions carefully

During the Test

✅ Maintain closed conditions

✅ Don’t move or touch the device

✅ Keep normal living habits

✅ Let the test run for the full period

After the Test

✅ Record the end date/time

✅ Mail your kit immediately

✅ Review results carefully

✅ Retest or mitigate if levels are high

✅ Retest every 2–3 years for safety

By following these steps carefully, you’ll ensure your radon test results are accurate — and your home stays healthy for years to come.

Conclusion: Testing Is Simple — Protection Is Priceless

Testing for radon isn’t complicated, but it must be done correctly.

A few careful steps before, during, and after your test can mean the difference between a false-safe reading and a life-saving discovery.

If you’re unsure about your results or live in a high-radon area like Ottawa, Toronto, or Calgary, it’s worth hiring a certified radon specialist.

Professional radon testing and mitigation can reduce levels by up to 99%, ensuring your family breathes safe, clean air.