Radon is produced in soil and rock and moves naturally upward through the ground. A house sitting on that ground is, in air pressure terms, slightly hungry: warm air rises and escapes at the top, and replacement air gets pulled in from wherever it can, including from below the floor. That is the mechanism. Soil gas follows the pressure difference into the building through whatever openings exist.
The openings are ordinary construction details rather than defects. Soil gas enters through the slab itself, through the joint where the foundation wall meets the floor, around sump openings, through utility penetrations and plumbing chases, and directly up out of an unsealed crawl space. None of that is unusual, and none of it means something was built badly. It simply means the floor of a house is not an airtight lid.
Radon has no odor, no color and no taste, and exposure to it produces no symptoms a person could notice. There is nothing to smell, nothing to see and nothing to feel, which is why the subject can only be handled with an instrument. That fact is often used to make people nervous. It should not be. It just means the question is answered by measurement rather than by observation, the same way you would not guess at the voltage in a wire.
It also means guessing from context is unreliable. Age of the house, price of the house, whether the basement is finished, whether the neighbors tested and what a regional map suggests are all weak predictors of a specific address. The EPA publishes an action level and Utah's Department of Environmental Quality publishes state guidance and maps, and those are worth reading, but they describe policy thresholds and regions. Your house gets described by your test.
A short-term test uses a device that stays in place for a matter of days. It is the fast answer, it is inexpensive, and it is what most transactions run on because it fits inside an inspection window. For a homeowner simply wanting to know, it is a perfectly reasonable first move and often the only test that ever gets run, because a result comfortably below the action level ends the inquiry.
Its limitation is built into its name. A few days is a small window, and indoor levels move with barometric pressure, wind, temperature, snow cover and how the house happens to be operated that week. A short-term result is accurate about the period it measured and only suggestive about the year. That is why a reading near the line usually prompts a second test rather than an immediate decision.
A long-term test leaves a device in place for months. Because it spans seasons and weather patterns, it averages out the swings that make a short-term result twitchy, and it produces a much better estimate of what an ordinary year in the house looks like. If your interest is the actual living conditions in your home rather than a number for a contract, the long-term test is the better instrument.
The trade-off is patience. You do not get an answer this week, which makes it a poor fit for a transaction deadline. The common pattern is to run a short-term test first for a quick read, then follow with a long-term test if the first result is ambiguous, near the published action level, or simply if you want a firmer basis before spending money on mitigation.
A test measures the house as it is operated, so the conditions during the test are part of the test. Closed-house conditions mean exterior doors and windows stay shut, beginning before the device is placed and holding until it comes out, with normal entry and exit allowed. Leave a window open for an afternoon and you have measured your ventilation habits rather than your house. Your contractor will tell you exactly what to avoid.
Placement follows the same logic. The device goes in the lowest level of the house that you actually occupy, positioned away from exterior walls, drafts, supply vents, fireplaces, and sources of heat or humidity, and left undisturbed. It should not be moved, covered, handled or relocated mid-test. A device in the wrong spot does not fail loudly; it just returns a number that quietly does not represent the room.
A result is a measurement, not a verdict. Compare it against the current EPA action level and the current guidance published by Utah's Department of Environmental Quality, both of which are available from the source and are the right places to read current figures. Below that threshold, there is nothing to install. At or above it, there is a well-understood fix, and the fix is a routine installation rather than a construction project.
The calm response to an ambiguous number is another test, not a purchase. Test again in a different season, or run a long-term device, and see whether the picture holds. The calm response to a clearly high number is to get quotes for sub-slab depressurization and to make sure a post-installation test is part of the scope. Either way, the sequence is the same: measure, then decide.
Test the lowest level of the house that you actually use. If the basement is living space, storage you spend time in, or a bedroom, that is where the device goes. If a lower level is entirely unused and sealed off from the rest of the house, the contractor may recommend testing the lowest occupied level instead. The rule is to measure the air people are in.
Yes, and in larger homes or homes with a slab section and a separate crawl space it is often sensible. Multiple devices describe a building more honestly than one device does, particularly when levels are separated by construction rather than just by stairs. Ask the contractor how many devices your layout warrants and what each one is meant to represent.
Mostly the obvious things: opened windows, a device that got moved, covered or knocked over, a test period interrupted by heavy ventilation, or a passive device that sat for days before reaching the lab. Continuous monitors log conditions and tend to reveal these problems on their own. If something went wrong, the fix is simple and unglamorous: run the test again.
Soil gas enters a house because the space under the floor is at a slightly higher pressure than the space above it, so gas moves upward through whatever openings exist. A…
Read the guide →Testing as a homeowner is leisurely. You place a device, you keep the house closed, you read the result whenever it comes and you decide at your own pace. Testing during a…
Read the guide →Test first, then decide. There is no fee to be matched.
Arrange a TestCounty, foundation type, and whether a deadline is involved is enough to start.