Radon is a radioactive gas that forms when uranium in soil, rock and water breaks down naturally. You cannot see it, smell it or taste it. Testing is the only way to know a home's radon level.
This page explains how a radon test works, which type to choose, and how to read the result. If you would like to talk to a local professional, call (928) 582-8914 and you will be connected with licensed and insured local contractors.
Why Prescott homes are worth testing
Prescott sits at about 5,400 feet in the Bradshaw Mountains. Just north of the city, the Granite Dells are made of granite about 1.4 billion years old, according to the Arizona Geological Survey. That granite has an unusually high uranium content, so homes built over it should be checked for radon.
The Arizona Geological Survey also notes that radon from the granite is a concern for people who build weather-tight homes on this rock. A tightly sealed, energy-efficient house can hold radon in. The highest indoor radon level ever measured anywhere was found in a home in the Granite Dells area near Prescott, according to KNAU Arizona Public Radio.
That does not mean every home has a problem. Any home can have one, new or old, with or without a basement. A test tells you where yours stands, whether it is a Victorian near downtown or a newer house toward Prescott Lakes or Willow Creek Road.
Short-term and long-term tests
There are two main kinds of radon test. The difference is how long the device stays in place.
- Short-term tests stay in place from 2 to 90 days. They give a snapshot of the radon level during that period.
- Long-term tests stay in place for more than 90 days. They better reflect the year-round average.
A short-term test is a common choice when you need an answer sooner, such as during a home sale. A long-term test makes sense when you want a picture that covers more of the year. Prescott has a pronounced summer monsoon season and dry spring and early summer months, so a longer test spans more of those changing conditions.
Closed-house conditions
For a short-term test, the home should be kept in closed-house conditions. That means windows and outside doors stay closed, except for normal coming and going. Prescott's day-to-night temperature swings average nearly 30 degrees, and it is natural to open windows to cool a house down. During a test, keep them shut so the result is not thrown off.
The testing professional will explain the details for your home. Ask about anything that might affect the test, such as fans or other equipment you normally run.
Where the test goes
A test belongs in the lowest lived-in level of the home. That is the lowest level you use regularly, such as a finished basement, a ground-floor living area or a bedroom. It is not a closet, crawl space or a spot near a drafty opening.
EPA recommends testing all homes below the third floor. Radon can enter through cracks in floors and walls, gaps around pipes and wires, sump pits, crawl spaces and other openings in the foundation. The device is placed to measure the air you actually breathe, not the air in the foundation itself.
What your result means
Radon is measured in picocuries per liter, written as pCi/L. EPA gives two clear reference points:
- At 4 pCi/L or higher, EPA recommends fixing the home.
- Between 2 and 4 pCi/L, EPA says homeowners should consider fixing it.
EPA calls radon the leading cause of lung cancer among people who have never smoked, and the second leading cause overall. That is why the result is worth acting on. If your number is at or above the action level, the next step is a reduction system. The mitigation page covers how those systems work, and the post-mitigation page covers retesting after one is installed.
Homes with private wells
Some homes outside the city center use private wells. Radon in well water can be released into the air when water is used, and gaps in a well casing can be a pathway for radon. Well water is tested separately from air. For most homes, radon in air is the larger concern, so an air test is the usual starting point.
Testing during a home sale
Radon tests are often done during the inspection period of a sale. If you are buying, a result from a previous owner may not reflect current conditions, especially after renovations. If you are selling, a recent test can answer a buyer's question before it comes up.
Choosing who does the test
Arizona does not run a state radon certification program. EPA recommends hiring a qualified radon professional, and the national certification programs are the National Radon Proficiency Program and the National Radon Safety Board. Ask any professional about their certification before you book.
Help is available across Prescott, the nearby towns of Prescott Valley, Chino Valley and Dewey-Humboldt, and Yavapai County. To set up a test, call (928) 582-8914. Cost depends on the home's foundation type, size and layout, so local professionals give a quote after looking at the home.