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Owning and renting5 min read

Can I turn off my radon system?

By Radon411 Editorial TeamUpdated How we research

Short answer

No. A radon fan should never be turned off: it must run continuously for the system to work. The fan draws radon from under the floor and vents it above the roof, and when a system stops venting, radon levels in the building rise. Running it only slightly raises the electric bill.

Next step: check the rules where you rent or let. Radon rules for rentals by state

A house usually sits at slightly lower air pressure than the soil, so it draws radon in. The fan reverses that by keeping a vacuum under the floor, and only while it runs.

If the fan seems noisy, broken or unnecessary, the answer is a call to the installer, not the switch. A low test result shows the system working with the fan on; retest at least every two years to be sure levels stay low.

What to do next: leave the fan on, check the warning device regularly, and call the installer if it shows a problem.

Why the fan has to keep running

Air pressure inside a house is usually a little lower than in the soil around the foundation, so the house acts like a vacuum and draws radon in through cracks and other openings. A radon system turns that around. Its fan, connected to suction pipes under the floor, draws radon from below the home and releases it outdoors, and at the same time creates a vacuum beneath the slab.

Cross-section of a house with a sub-slab depressurization system: soil gas drawn from beneath the slab into a suction point, up a vent pipe, through a fan outside the living space and out above the roofline.
Read this figure as text
Sub-slab depressurization system in a house cross-sectionGround levelLiving spaceBasement12345
  1. Soil gas drawn from beneath the slab
  2. Suction point through the slab
  3. Vent pipe
  4. Fan, outside the living space
  5. Discharge above the roofline
A sub-slab system: the fan keeps a vacuum under the floor and vents the radon above the roof, but only while it runs.

Everything depends on that fan. The guidance is blunt: the fan should never be turned off; it must run continuously for the system to work correctly. When a system stops venting, as when ice blocks the pipe in a long cold spell, radon levels in the building increase.

Reasons people want it off, and what to do instead

Common reasons to switch off a radon fan, and better answers
ReasonWhat to do instead
The electric billFan systems slightly raise the electric bill, and most systems lose some heated or cooled air; that is the running cost of a system that works
Noise or vibrationCall the installer; flexible air-tight couplings are used to reduce vibration and noise transmission
The last test was lowA low result shows the system working with the fan on; keep it on and retest at least every two years
Windows open in summerOpen windows lower radon only temporarily; levels most often return within about 12 hours of closing up
A renovationAsk the radon contractor whether the changes could void any warranties, and retest in the lowest lived-in area afterwards
The fan seems to have failedCheck that the monitor tubing is connected and not kinked and that the fan has power, then call the installer

Many systems have no switch for a reason: building guidance calls for radon fans to be wired to an unswitched electrical junction box, and systems are clearly labeled so that no one changes them by accident. If an air exchanger is part of the system, it has to keep running too.

Signs the system has stopped

Because a stopped fan is silent about radon, every active system has a warning device placed where it can be seen or heard easily. It may be a liquid gauge, a sound alarm, a light or a dial gauge, and in Minnesota every system has two: a u-tube manometer and an active notification monitor.

Reading the warning devices
What you seeWhat it means
U-tube manometer fluid at its marked levelThere is suction in the pipe; it does not measure radon
Fluid levels evenThe fan stopped working or another part of the system is not working properly
Active notification monitor alarm, light or soundThe system has stopped working
Fluid even and an alarm during a long cold spellPossibly a system freeze-up: ice in the pipe stops the radon venting, and the pipe may need insulating

Check the devices regularly; Minnesota asks for monthly checks, including the monitor's power source. Before calling for service, make sure the monitor tubing is connected and not kinked and that the fan has power. If there is still a problem, call the installer. Fans may last five years or more and then need repair or replacement.

Passive systems: the one kind with no fan

Some newer homes have a passive radon system: a vent pipe from under the slab up through the warm part of the house and out the roof, with no fan. The natural stack effect pulls soil gas up and out. There is nothing to switch off, and an outlet or junction box is often left near the pipe so a fan can be added.

Passive and active radon systems
AspectPassive systemActive system
What moves the soil gasThe natural stack effectAn in-line fan in the vent pipe
Can it be switched off?Nothing to switch offNo; the fan must run continuously
When to change itIf a test is high, add a fan to make it activeIf a test is high, call the contractor to adjust it

Turning a passive system into an active one is designed to be easy: the fan goes into the existing vent pipe. More is in how to install a radon mitigation system in new construction.

Questions about switching off a radon system

Can I turn off my radon fan in the summer?

No. The fan must run continuously for the system to work, in every season. Opening windows lowers radon only for as long as they stay open.

Can I unplug the radon fan while I am away?

The guidance makes no exception: the fan should never be turned off. A radon system is meant to run all the time.

Does a radon fan use a lot of electricity?

Fan systems slightly increase the electric bill, and most systems lose some heated or cooled air, which can add to utility costs.

What happens if my radon fan stops?

The system stops venting radon, and levels in the building can rise. The warning device should show it: even fluid in the manometer or an alarm. Check power and tubing, then call the installer.

Why is there no switch on my radon fan?

Building guidance calls for an unswitched junction box for radon fans, and systems are labeled, so the fan is not turned off or changed by accident.

How long does a radon fan last?

Fans may last five years or more, and manufacturer warranties tend not to exceed five years. See the radon fan guide.

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