Understanding Radon: How Measurement Changes Where You Live, Work, and Learn

Radon is the leading cause of lung cancer among non-smokers and the second leading cause overall. Despite being a significant public health risk, it often goes undetected because it is invisible, odorless, and tasteless.

Where We Live: Measuring Radon in Homes

In a residential setting, the goal is to capture a general snapshot of the air you breathe most frequently.

• Placement: Place at least one detector in the largest "lived-in" area on the lowest occupied level (e.g., a finished basement or a ground-floor living room).

• Supplementary Testing: You can test individual rooms to see how radon dissipates across floors, but this should supplement—not replace—a central area test.

• When to Test:
  • If you have never tested before.
  • When buying or selling a home.
  • Following a major renovation or construction project.
  • Every 2 years (per EPA recommendations), as levels can shift over time.
  • Avoid these 3 radon measurement mistakes.

Where We Work: Measuring Radon in Office Buildings

Office buildings are larger and more complex than homes, requiring a more strategic approach to testing.

• Coverage: Test all occupied rooms in contact with the ground. Additionally, test 10% of upper-floor rooms.

• Large Spaces: Use one detector for every 2,000 square feet (U.S.) or 200 square meters (Canada).

• The HVAC Factor: Most offices turn off or reduce HVAC systems during evenings and weekends. This causes radon levels to spike when the building is empty.

• Recommendation: Use a continuous radon monitor. This allows you to distinguish between high levels at night and the actual levels you are exposed to during the 9-to-5 workday.

Where We Learn: Measuring Radon in Schools

Testing in schools requires strict adherence to schedules to ensure the data reflects the environment students and teachers actually experience.

• Timing: Testing must occur during normal school hours when the building is occupied. Avoid holidays, summer breaks, or long weekends.

• Protocol: ANSI/AARST standards require testing every occupied room on the ground floor and 10% of rooms on upper floors.

• Retesting: Retest at least every five years if levels are below the actionable limit of 4.0 pCi/L (U.S.) or 200 Bq/m³ (Canada). Retest sooner if the building undergoes HVAC upgrades, foundation work, or new classroom construction.

Why the Differences Matter

In homes, there is typically more consistent ventilation. However, schools and office buildings have variable ventilation schedules.

• HVAC schedules: Commercial and school buildings use sophisticated HVAC systems that are programmed to shut down or reduce airflow on nights and weekends to save energy.

• Pressure changes: When the air is "off" at night, the building is no longer pressurized, allowing radon to seep in more easily from the soil. When the system kicks on in the morning, it dilutes the radon.

• A "false high": A radon test kit left in an office from Friday to Monday might show a "high" reading because it sat in a stagnant building all weekend. However, the actual exposure for workers or students during the day, when the fans are running, might be well below the safety limit.

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