What Is Radon? A Plain Twin Cities Home Guide

What is radon?

Radon is a radioactive gas that forms naturally when uranium and radium in soil and rock break down. You cannot see, smell, or taste it. Outdoors, it usually disperses. Indoors, it can enter through openings that connect a building to the ground and accumulate in the air people breathe.

The Minnesota Department of Health radon overview describes radon as a serious indoor air concern throughout the state. The EPA radon overview explains the same basic point nationally: every home can have a radon problem, and testing is the only way to learn the level in a particular home.

How does radon enter a home?

Air pressure inside a home is often lower than pressure in the soil below and around the foundation. That difference can draw soil gas indoors. Common entry paths include cracks in a slab or foundation wall, gaps around pipes, floor drains, sump openings, construction joints, and exposed soil in a crawl space.

A newer foundation does not guarantee a low result. An older drafty home does not guarantee a high one. Building materials, foundation details, weather, ventilation, heating equipment, and soil conditions all affect the amount that enters and remains indoors.

This is why a result from the home next door cannot stand in for your result. Two buildings on the same block can have different entry paths and indoor pressure patterns. County maps describe broad potential, not a reading for an address.

Why does long-term exposure matter?

When radon decays, it creates radioactive particles that can be inhaled. Those particles can damage lung tissue over time. EPA identifies radon as the second leading cause of lung cancer in the United States and the leading cause among people who do not smoke. Smoking and radon together create a higher risk than either exposure alone.

The purpose of testing is not to create panic over a single moment. It is to learn whether the level in a home calls for follow-up and, when confirmed, action. The EPA Citizen’s Guide to Radon explains the health context, testing choices, and reduction options in one public guide.

What do Minnesota’s numbers mean?

Minnesota uses EPA’s action level of 4.0 picocuries per liter, written as 4.0 pCi/L. According to MDH testing and result guidance, the first screening result determines the follow-up:

• From 0 to 1.9 pCi/L, retest every 2 to 5 years.
• From 2 to 7.9 pCi/L, perform a long-term follow-up test.
• At 8 pCi/L or higher, perform another short-term test.

The approved follow-up result is what guides the decision. MDH recommends mitigation at 4.0 pCi/L or higher and says to consider mitigation from 2.0 to 3.9 pCi/L.

These thresholds do not mean that 3.9 is harmless or that one brief reading of 4.0 proves a lasting condition. They provide a consistent decision path. Following the full path is more useful than reacting to one afternoon on a display.

Where do reusable monitors fit?

A continuous consumer monitor can show how radon changes across days, weeks, rooms, weather, and heating patterns. It can be moved, reused, and shared. That makes it useful for awareness and for understanding why one short snapshot may differ from another.

MDH does not recommend a consumer digital monitor as the device that decides a real estate transaction or a mitigation decision. Use an approved mail-in test or a Minnesota-licensed measurement professional for that decision. The site’s monitor comparison keeps those roles separate and shows the three reusable models currently featured.

The guide to monitors and mail-in kits explains which tool fits a trend, first screen, long-term follow-up, or sale test.

How should a Minneapolis household start?

Start with the Minnesota testing steps. Use the lowest level that is regularly occupied, follow the device instructions, and maintain closed-home conditions for a short test. Heating season is often a useful time because the home is closed more consistently, but severe or unusually windy weather is a reason to wait.

If you need a low-cost approved test, check the current local kit options. Program prices, stock, mailing rules, and residency limits change, so the official city, county, or MDH page should make the final call.

If you already have a reusable monitor, record the room, dates, ventilation changes, and averages. A trend without placement notes can be hard to interpret. The monitor sharing checklist provides a simple way to lend a device without losing that context.

The useful takeaway

Radon is a naturally occurring gas that can build up indoors, not a judgment about a neighborhood or a home. Maps and nearby results provide context, but only a test provides a result for your home. A reusable monitor helps explain patterns. Approved testing provides the number Minnesota uses for a sale or mitigation decision.