Reviewed and updated September 13, 2026. This article provides general public-health and referral guidance, not testing, medical, legal or engineering advice.
An active system needs the fan to run continuously
Active radon mitigation depends on a powered fan creating negative pressure in the soil-gas collection system. During a power outage, that active suction stops. EPA guidance says the fan should run continuously for the system to work correctly, so a prolonged outage can interrupt the reduction the system normally provides.
For a home in Elmira, Horseheads or Corning, the sensible response after power returns is to verify the system rather than panic over the outage itself. Indoor radon can change with time and conditions, and the effect of one outage cannot be predicted from duration alone without measurement.
After power returns, check the warning device and fan behavior
Look at the manometer, alarm, light or other warning device that normally shows system operation. Compare it with the normal operating state. Listen for the fan from a safe location and note whether it sounds normal, unusually loud or completely silent.
If the breaker or electrical protection device immediately trips again, the fan does not restart or the warning device stays in a failure condition, do not improvise electrical repairs. Contact the installer or another qualified professional. The manometer guide explains how to interpret the common pressure gauge without confusing it with a radon reading.
Do not assume that a spinning fan means the whole system is fine
Power restoration can restart the fan while another problem remains. A damaged fan bearing may become noisy. A loose coupling or piping issue may alter performance. The warning device may show a different pressure than before the outage. Those changes deserve attention even if the fan is technically running.
Likewise, a normal manometer only shows pressure at that point in the system. It does not measure indoor radon. If you have reason to believe the system was off for an extended period or the operating condition changed, radon testing can verify that indoor levels are again controlled.
Continuous monitors can show recovery—but use averages carefully
If you already use a continuous radon monitor, you may see the indoor reading rise while the fan is off and decline after it restarts. That pattern can be informative, but hourly data should still be interpreted in the context of longer averages and proper test conditions.
Do not decide that a system failed permanently from one spike immediately after an outage. If the average remains elevated after the fan has resumed normal operation, or if the system warning device is abnormal, move to a service evaluation and a protocol-based follow-up test rather than waiting for the graph to fix itself.
Document the outage if it affected testing or a home sale
A power interruption during a short-term radon measurement can affect the conditions being evaluated when an active system is supposed to be operating. Record when the outage began, when power returned and whether the fan restarted. Share that information with the testing professional before relying on the result in a transaction.
If service or fan replacement is needed, follow it with appropriate radon testing. The retesting guide explains the post-mitigation testing window and why system repairs should end with a measurement, not just a restored hum.
Sources
Primary guidance used for this article
We use government and public-health sources, distinguish historical datasets from current household measurements, and do not invent local results. Read our editorial policy.