Is the system safe to leave running all year?
Why the system has to run year-round
Radon is a continuously-generated gas. The radium in the rock under your home is always decaying. The gas is always being produced. Without something pulling it out, it always finds its way up through the soil and into the basement air.
Indoor radon does swing seasonally. The Minnesota Department of Health data shows a statewide winter mean of 4.3 pCi/L versus a summer mean of 3.4 pCi/L. But "lower in summer" still means well above the EPA action level for most southeast Minnesota homes. A home that reads 2.0 pCi/L in summer with the system running could read 6.0 pCi/L without it.
The fan being off for an hour while you swap it out is fine. The fan being off for a season is not.
Power use and operating cost
The fan is the only continuous power draw on a mitigation system. There is no compressor, no pump, no heating element. Typical numbers:
- Small inline fan (50 W): roughly $5 to $6 per month, $60 to $75 per year.
- Standard inline fan (90 W): roughly $10 to $12 per month, $120 to $145 per year.
- Larger inline fan (150 W): roughly $16 to $20 per month, $200 to $240 per year.
Those are at Rochester Public Utilities residential rates. The fan runs all 8,760 hours of the year, so the monthly bill is steady. There is no startup surge to worry about.
Fan reliability
Inline radon fan bearings are rated for continuous duty. Real-world life is about 8 to 12 years before the bearings get loud or the suction drops. Most homeowners do not notice the gradual decline. The manometer gauge on the pipe is the early indicator if the two fluid columns are coming closer together than they used to.
When the fan does fail, it usually fails gradually rather than suddenly. The gauge drifts, the suction drops, and the basement radon creeps back up over weeks or months. That is why re-testing every two years is the recommended cadence, not just relying on the gauge.
Routine maintenance
A mitigation system needs almost no upkeep.
- Check the gauge once a month. Quick visual. Two fluid levels should be at different heights. If they sit at the same level, the fan is off or has failed.
- Re-test every two years. Short-term test or continuous monitor. EPA and AARST both recommend this cadence.
- Re-test after any major home change. Renovation, new HVAC, new sump cover, basement remodel.
- Plan for a fan swap around year 10. Some last longer, some need it sooner. The fan replacement is straightforward.
That is the entire maintenance list.
What changes the answer
- Fan placement. An exterior-mounted fan in southeast Minnesota cold gets a few colder bearings days than an attic-mounted fan. Either is fine, but attic mounts tend to outlast exterior mounts by a year or two on average.
- How the fan is wired. A fan on a switched circuit can be turned off by accident. We hard-wire mitigation fans to dedicated circuits where possible.
- Power outage recovery. The fan restarts automatically when power returns. No homeowner action needed.
- Backup power. Not standard. If you have a whole-home generator, the radon fan should be on a circuit that the generator covers.
The one time we recommend turning it off
During a fan swap, repair, or any work on the system itself. Otherwise, leave it running.
Sources
- AARST/ANSI standard SGM-SF (residential radon mitigation), continuous operation requirement.
- U.S. Environmental Protection Agency, Consumer's Guide to Radon Reduction.
- Rochester Public Utilities residential electric rate schedules.