Radon is a naturally-occurring soil gas that mostly occurs in rocky soil. It rises into buildings through small cracks in the lowest level floor – usually through the floor of the basement or crawl space, or through the ground floor if the building is built atop a slab. Long-term exposure to radon has been linked to lung cancer. Although the EPA New York State radon map shows that the NYC metro area is the lowest-incidence area, radon testing is universally recommended by real estate professionals, as pockets of elevated radon levels do exist.
The most common and simplest radon test involves leaving one or more testing canisters set up in a sealed room (no running fans of any sort and all windows/doors closed) at the lowest level in the building undisturbed for at least 48 hours (follow manufacturer’s instructions). They can be purchased in a hardware store or found by typing “radon test kit” into a search engine. They are usually $15-$25 each, which includes the lab analysis. After 48 hours, they must be collected and sent to the lab. These short-term tests have two shortcomings:
First, performing a radon test in a building you don’t own can be challenging, as the test must be left undisturbed in a sealed room. When you don’t have control over that environment, tampering could occur, unbeknownst to you.
Second, the 48-hour test is a snapshot, which may not provide the full picture, because radon levels can fluctuate over the course of the year. Negative results from a single test of this type cannot be relied upon as a final assurance that the house is radon-free. Therefore, multiple canister tests should be done during different times of year, or a continuous data logger should be set up to monitor radon levels over a longer time period.
If you perform a radon test yourself, be sure to use testing devices that are NEHA- or HRSB-approved. The EPA action level for radon measurements is 4 picocuries per liter (pC/l), although some studies recommend action at levels between 2 and 3 pC/l. Such action would take the form of a properly designed radon mitigation system. Mitigation systems do not involve complicated equipment and are generally not prohibitively expensive.
Read more on what the EPA says about radon here: http://www.epa.gov/radon/