The only way to know your Sioux Falls number
Radon has no smell, color, or taste. A test is how you find out where your home stands.
Why testing is the only answer
You cannot see, smell, or taste radon. No stain shows up on the wall, no odor drifts up from the basement. A house at 20 picocuries per liter feels exactly like a house at 1. The EPA and the state radon program recommend testing for one plain reason: measurement is the only way to know.
Your neighbor’s result doesn’t answer the question either. Two houses on the same Sioux Falls block can read far apart, because the gas follows cracks and soil pockets that don’t respect lot lines.
Around here, testing usually happens at a few predictable moments. A home inspection during a sale turns up a number; that’s the most common trigger. New arrivals test because they’ve heard eastern South Dakota runs high. And homeowners test in winter, when the house has been shut tight for weeks and readings tend toward their honest worst. If the number comes back high, mitigation is the well-worn fix, and it ends with a retest that proves the level came down.
Short-term or long-term — which test fits
Short-term kit
- How long it runs
- 2 to 7 days
- What it's for
- A first screen of the home
Continuous monitor
- How long it runs
- About 48 hours
- What it's for
- Home sales and quick decisions
Long-term test
- How long it runs
- 90 days or more
- What it's for
- A true year-round average
| Test type | How long it runs | What it's for |
|---|---|---|
| Short-term kit | 2 to 7 days | A first screen of the home |
| Continuous monitor | About 48 hours | Home sales and quick decisions |
| Long-term test | 90 days or more | A true year-round average |
Radon is measured in picocuries per liter. Any test that reads at or above the EPA action level of 4 pCi/L deserves a follow-up.
Testing inside a home sale
A transaction test isn’t a hardware-store kit on the furnace room shelf. Deals need results fast and both sides need to trust them, so real-estate testing follows tighter protocols. Continuous monitors that log hourly readings over about 48 hours are the usual tool. They flag power interruptions and unusual swings, which answers the tamper question before anyone asks it.
Closed-house conditions still apply: windows shut, doors used normally, for 12 hours before and during the test. An inspector or agent will usually schedule the monitor alongside the general inspection so the deadline doesn’t get squeezed.
Some states license who can test and who can mitigate in a transaction. South Dakota currently doesn’t, which makes the device protocol and the written report carry the weight. The details of how radon fits a South Dakota deal (disclosure, negotiation, timing) are covered in radon and home sales.
Get a number you can act on
If the number comes back high
First: nothing about your house is broken. High readings are common across the Sioux Falls area, and the path forward is short and well marked.
If the result landed near the action level, say between 4 and 8 picocuries per liter, published guidance suggests confirming it before spending money. Levels swing with weather and season, and a second test, or a long-term test, tells you whether the first number was the real story. A monitored transaction test is generally solid enough to act on as-is, and in a home sale the calendar usually decides for you.
Well above the action level, confirmation matters less. The fix is the same either way: a mitigation system, sized to the house, verified by a follow-up test. There’s a calm walkthrough of the whole decision at your test came back high, and the fix itself is laid out plainly on the mitigation page.
The one thing not to do is nothing. A number you’ve confirmed and fixed is worth more than a number you’ve been meaning to think about.
Frequently Asked Questions
When should a home get tested?
Any home that's never been tested is due, and the EPA suggests retesting every few years even after a low result. Testing also makes sense after finishing a basement, after major foundation work, or before putting a house on the market.
What are closed-house conditions?
Windows and exterior doors stay shut for 12 hours before and during a short-term test, apart from normal coming and going. That keeps outdoor air from diluting the sample and gives a reading you can trust.
Are store-bought kits any good?
They're a legitimate way to screen a home when the instructions are followed carefully. Real-estate transactions and pre-mitigation decisions typically call for professional testing or a continuous monitor. An elevated kit result is worth confirming before you act on it.
How do results come back?
It depends on the device. Continuous monitors can produce a report shortly after pickup, while mailed-in kits go through a lab first. Either way the result is a written number you can compare against the action level and keep with the house.