How Long to Test for Radon: Short-Term vs Long-Term Testing

Short-term testing:

• •Duration: 2 to 90 days
• •Fastest way to get results
• •Good for initial screening
• •Required for real estate transactions

Long-term testing:

• •Duration: More than 90 days
• •More accurate annual average
• •Better represents seasonal variation
• •Recommended for non-urgent situations

Common short-term test types:

• •Charcoal canisters (2-7 days)
• •Alpha track detectors (2-90 days)
• •Electret ion chambers (2-90 days)
• •Continuous monitors (2-90 days)
• •Charcoal liquid scintillation (2-7 days)

Advantages:

• •Fast results for decision-making
• •Lower cost
• •Good for real estate transactions
• •Suitable when quick action is needed

Limitations:

• •Less representative of annual average
• •Can be affected by seasonal variations
• •May require follow-up testing
• •Weather and testing conditions matter more

When to use short-term testing:

• •Initial home screening
• •Real estate purchase or sale
• •Before major renovation
• •When quick results are essential
• •Before conducting long-term test

Common long-term test types:

• •Alpha track detectors (90+ days)
• •Electret ion chamber detectors (90+ days)

Advantages:

• •Most accurate annual average
• •Accounts for seasonal variations
• •Better represents year-round exposure
• •Less affected by weather fluctuations
• •More reliable for mitigation decisions

Limitations:

• •Takes longer to get results
• •Requires patience
• •May delay decision-making in urgent situations

When to use long-term testing:

• •Non-urgent situations
• •After initial short-term test
• •To verify mitigation system effectiveness over time
• •For most accurate assessment
• •When you can afford to wait

Path A: Long-term follow-up

• •Conduct a 90+ day test
• •Provides better understanding of year-round average
• •Fix your home if result is 148 Bq/m³ (4 pCi/L) or higher

Path B: Second short-term follow-up

• •Conduct another 2-90 day test
• •Provides faster results
• •Fix your home if average of both tests is 148 Bq/m³ (4 pCi/L) or higher

Step 3: Take Action

• •Long-term test ≥ 148 Bq/m³ (4 pCi/L): Fix your home
• •Average of two short-term tests ≥ 148 Bq/m³ (4 pCi/L): Fix your home
• •Result below 148 Bq/m³ (4 pCi/L): Consider retesting periodically

Closed-house conditions (required for 2-3 day tests):

• •Close all windows and exterior doors 12 hours before testing
• •Keep closed throughout test period
• •Exception: Normal entry and exit

What you CAN do during testing:

• •Operate heating and air conditioning (recirculating air)
• •Use small exhaust fans for short periods
• •Enter and exit normally
• •Conduct normal daily activities

What you should NOT do during testing:

• •Open windows or exterior doors for extended periods
• •Operate whole-house fans
• •Use window air conditioners
• •Operate fans that bring in outside air
• •Operate fans that exhaust large volumes of air

Weather considerations:

• •Avoid 2-3 day tests during severe storms
• •Avoid testing during unusually high winds
• •Weather less critical for longer tests

Recommended approach:

• •Use short-term testing only
• •Conduct two short-term tests simultaneously (placed 10 cm / 4 inches apart)
• •Minimum 48 hours duration
• •Use devices from qualified laboratories
• •Consider hiring professional tester

Why simultaneous testing:

• •Provides faster results than sequential tests
• •Increases confidence in results
• •Meets typical closing timelines
• •Acceptable for real estate decisions

Timeline considerations:

• •2-day test: Results in ~1 week
• •4-7 day test: Results in ~2 weeks
• •Allow time for lab analysis
• •Build in time for mitigation if needed

Professional testing advantages:

• •Faster turnaround
• •Greater credibility with buyers/sellers
• •Proper protocol followed
• •Documentation for transaction

1. Heating season (higher radon):

• •Closed windows and doors
• •Greater indoor-outdoor temperature difference
• •Increased "stack effect" drawing radon in
• •Typically highest levels

2. Cooling season (may be lower):

• •More ventilation from open windows
• •Less temperature difference
• •Different air pressure patterns
• •May show lower levels

3. Transitional seasons:

• •Variable conditions
• •Moderate radon levels
• •Can be unpredictable

Short-term tests:

• •May catch seasonal high or seasonal low
• •Winter test might show higher level than annual average
• •Summer test might show lower level than annual average
• •Single test may not represent year-round exposure

Long-term tests:

• •Average out seasonal highs and lows
• •Represent true annual exposure
• •More reliable for protection decisions

Retest every 2-5 years if:

• •Initial test was below action level
• •No changes to home structure
• •You want to monitor for changes

Retest immediately if:

• •Major structural renovation completed
• •New living space created (finished basement)
• •Foundation repaired or modified
• •Heating/cooling system changed significantly
• •You begin using a lower level (e.g., finishing basement)

After mitigation:

• •Test within 30 days of system installation
• •Test annually to verify continued effectiveness
• •Test after any system modifications
• •Test if warning device indicates problem

Testing protocol for retesting:

• •Use same type of test device when possible
• •Test in same location
• •Use same conditions (closed-house)
• •Compare results to previous tests

Why retest:

• •Radon levels can change over time
• •Home modifications affect radon entry
• •Mitigation systems need monitoring
• •New geology information may emerge
• •Peace of mind for your family's safety

Use 2-4 day short-term test when:

• •Real estate transaction in progress
• •Urgent decision needed
• •Initial screening before long-term test
• •Verifying immediate post-mitigation results
• •Time-sensitive situation (impending sale, rental)

Use 7-90 day short-term test when:

• •Want more reliable result than 2-4 day
• •Can afford slightly longer wait
• •Following up on marginal initial result
• •Not in immediate time pressure
• •Want better seasonal representation

Use long-term test (90+ days or year-long) when:

• •No time pressure for results
• •Want most accurate annual average
• •Following up on short-term test
• •Verifying long-term mitigation effectiveness
• •Making permanent mitigation decision
• •Current radon level is uncertain or borderline

Combination approach (recommended):

• • - Second short-term if urgent
• • - Long-term if time allows

If first test shows very high level (≥ 740 Bq/m³ / 20 pCi/L):

• •Don't wait for long-term test
• •Conduct second short-term test immediately
• •Begin mitigation process promptly
• •Err on side of faster protection

If first test shows marginal result (111-185 Bq/m³ / 3-5 pCi/L):

• •Long-term test provides better information
• •Helps avoid unnecessary mitigation
• •Helps ensure adequate protection
• •Worth the wait for accurate data