Understanding Your Radon Test Results – What Do the Numbers Mean?

You’ve taken the first important step against radon exposure by testing your home. But what do those test results really mean and what level is considered safe? Radon test reports can be confusing if you’re not familiar with the different measurement units, technical terms, and guidelines. This article clearly explains how to interpret radon test results from home test kits or professional monitors so you understand your risks and next steps.

The Dangers of Radon Exposure

Radon is an odorless, radioactive gas that arises naturally from uranium decay underground. It seeps into homes through cracks and openings in foundation floors and walls where it accumulates in indoor air, especially in lower levels. As radon decays further, it releases radioactive particles that lodge in our lungs when inhaled, damaging lung tissue and eventually leading to cancer.

Radon is the second leading cause of lung cancer in the U.S. after smoking. The Surgeon General estimates radon causes about 21,000 lung cancer deaths per year. It is the number one cause of lung cancer in non-smokers. Radon can easily go undetected without testing, silently harming you and your family’s health.

Key Radon Measurement Units

Radon test devices measure the concentration of radon gas in the air, usually in your home’s basement or main floor. The results are reported in units of radioactivity per volume of air, specifically picocuries per liter (pCi/L).

A picocurie is a measurement of radioactive decay. One picocurie means two radon atoms decay every minute in each liter of air. Most U.S. radon tests are reported in pCi/L.

Outside the U.S., Becquerels per cubic meter (Bq/m3) may be used instead. 37 Bq/m3 equals 1 pCi/L for easy conversion between units. Knowing the units used is vital for understanding health risks.

EPA & WHO Radon Guidelines

Two major public health organizations have established the following radon risk guidelines and recommended levels for action:

  • EPA (U.S. Environmental Protection Agency)
    Recommended Fix Level: 4 pCi/L
    The EPA suggests homeowners take action to reduce indoor radon levels that measure at or above 4 pCi/L.
  • WHO (World Health Organization)
    Reference Level: 2.7 pCi/L (100 Bq/m3)
    The WHO’s guidelines are slightly stricter at 2.7 pCi/L. Some U.S. states have adopted this lower level as their recommended radon action threshold.

While no level of radon exposure is safe, risks increase as concentrations rise above these guidelines.

Interpreting Short-Term Test Results

Short-term tests remain in your home for 2 to 90 days. Detectors include charcoal canisters, alpha track, liquid scintillation, and continuous monitors. Average short-term results over 2-7 days provide a general idea of radon levels. However, concentrations fluctuate daily and seasonally.

The EPA recommends follow-up long-term testing after initial short-term results. If short-term results are over 4 pCi/L (or 2.7 pCi/L), you should still mitigate immediately and verify with long-term monitoring. An initial short-term test alone should not be used for making major mitigation decisions.

Understanding Long-Term Test Results

Long-term tests remain in your home for more than 90 days to a full year. This provides a more accurate average radon level as fluctuations are minimized over time. The most precise long-term detectors are continuous radon monitors. Exposure for a full year gives the best data on actual radon health risks for that home.

Long-term test results are better indicators of when mitigation should be implemented. If your long-term average radon level is at or above 4 pCi/L, install a radon mitigation system right away. Long-term testing also lets you measure mitigation system effectiveness by comparing before and after results.

What if Results are Near 4 pCi/L?

Some homes may have test results ranging from 2 to 4 pCi/L, just under EPA guidelines. The EPA still recommends considering mitigation when results are between 2 and 4 pCi/L, as there is no known safe radon level. Compare the costs against radon health risk reduction benefits. You can also make smaller ventilation improvements to try reducing levels. Retesting annually is important even if initially under 4 pCi/L.

Next Steps If Results are High\
Immediately contact a certified radon mitigation contractor if your test result, especially long-term, is 4 pCi/L or higher (2.7 pCi/L in some states). A proper radon mitigation system can reduce levels by up to 99%. Get quotes from qualified radon contractors so the system can be professionally installed as soon as possible.

Radon testing provides vital information to guide smart decisions about protecting your household. Knowing how to properly interpret radon test results empowers you to take swift action when risks are high. Review radon data carefully, utilize public health guidelines, and breathe easier knowing your home’s air is safe.

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