NRPP RMI key terms

The unit used to report radon concentration in air, equal to one trillionth of a curie per liter. US programs commonly use 4 pCi/L as an action level and 2 pCi/L as a consideration level.

The SI unit of radon activity concentration, meaning one radioactive decay per second in a cubic meter of air. Conversion: 1 pCi/L equals 37 Bq/m3, so 4 pCi/L is about 148 Bq/m3.

A measure of the potential alpha energy from short-lived radon decay products in one liter of air, defined as 130,000 MeV of alpha energy. Used mainly in mining and occupational exposure contexts rather than residential testing.

An occupational exposure unit equal to exposure to one working level for 170 hours. It accumulates over a work history and is used to express miner and other occupational radon progeny dose.

The radon concentration at which a testing program recommends mitigation or further evaluation. In US residential programs it is 4 pCi/L, while 2 pCi/L is a level at which mitigation should be considered.

A naturally occurring radioactive noble gas produced by decay of radium-226 in soil and rock. It is colorless, odorless, chemically inert, and its decay products deliver most of the alpha dose to lung tissue.

Short-lived solid isotopes formed when radon decays, including polonium-218, lead-214, bismuth-214, and polonium-214. These attach to airborne particles and deposit in the lung, where their alpha emissions cause damage.

The chain of radioactive decays beginning with uranium-238 and ending with stable lead-206. Radium-226 and then radon-222 appear partway through the chain, which is why radon is widespread in soils containing uranium.

A radioactive metal in the uranium-238 decay series that decays to radon-222 with a half-life of about 1,600 years. Its concentration in soil and building materials largely determines how much radon is generated nearby.

The time required for half the atoms of a given radionuclide to decay. Radon-222 has a half-life of about 3.8 days, which governs how long detectors must sample and how quickly concentrations respond to ventilation.

The specific radon isotope produced in the uranium-238 series, with a half-life near 3.8 days. It is the isotope of concern in buildings and the one measured by standard radon tests.

The ratio of measured radon decay product activity to the radon activity that would exist at full secular equilibrium. Values below 1 mean progeny are partially removed by ventilation, plateout, or filtration relative to the parent gas.

A radon measurement lasting from a few days to about 90 days, often using charcoal or electret devices. It gives a quick screening result but is more vulnerable to day-to-day weather and ventilation swings than a long test.

A radon measurement conducted for more than 90 days, typically with alpha track or electret detectors. Because it averages seasonal variation, it better estimates the year-round average concentration that occupants actually experience.

A test protocol requiring exterior doors and windows to stay closed, typically for 12 hours before and throughout a short-term test. It standardizes conditions so results reflect indoor radon without unusual ventilation.

The rules for locating a detector so it samples representative indoor air, including height above the floor, distance from walls and heat sources, and avoiding bathrooms, kitchens, and crawl spaces. Correct placement protects result validity.

A short-term passive device in which activated charcoal collects radon, which is later measured by gamma counting. It is inexpensive and sensitive but integrates only a few days and requires prompt return to the lab.

A passive detector in which alpha particles from radon and progeny leave etched tracks in a plastic film, counted after chemical etching. It is suited to long-term tests of three months or more and is relatively insensitive to humidity.

A passive device that measures radon by the voltage change of a charged electret as ionizing radiation discharges it. It can serve short- or long-term tests and is read by measuring the electret voltage before and after exposure.

An electronic instrument that samples air and reports radon concentration at intervals, producing a time record. It is used for short-term tests and for diagnostics such as checking for tampering or unusual concentration patterns.

The field procedure of placing, documenting, and later retrieving a detector, including recording start and stop times, location, and serial number. Poor deployment records can invalidate an otherwise good measurement.

A documented record tracking a detector from deployment through shipment and laboratory analysis, showing who handled it and when. It supports defensibility of results and helps detect lost, swapped, or mishandled devices.

A written plan describing measurement objectives, methods, calibration, audits, and data quality indicators for a radon project. It documents how the program will demonstrate that results meet required accuracy and precision.

A device of known radon exposure, prepared by a reference laboratory, that is analyzed as if it were a field sample. Spike results reveal bias and are a standard external check on laboratory and device performance.

Two detectors exposed side by side at the same location for the same period to assess precision. The difference between their results estimates measurement uncertainty and flags field or laboratory problems.

A performance check in which the analyst does not know the true value or identity of the sample. Blind tests reduce bias in proficiency evaluation and are often required for device approval programs.

An external evaluation in which a laboratory or measurement provider analyzes samples of unknown value and is scored against reference results. Passing demonstrates acceptable accuracy compared with peers and reference standards.

The process of comparing an instrument's response with a known reference source and adjusting or documenting the relationship. Continuous monitors and other active instruments need periodic calibration to remain within acceptable accuracy.

The closeness of repeated measurements of the same quantity to one another, expressed as a standard deviation or relative percent difference. It is separate from accuracy, which describes closeness to the true value.

The closeness of a measured value to the true or reference value, often expressed as relative percent error or bias. A measurement can be precise yet inaccurate if a systematic offset exists.

Features and review practices that reveal whether a detector was moved, opened, or exposed to abnormal conditions during a test. Continuous monitors may record motion, temperature, or unusual concentration patterns that suggest interference.

Any condition that distorts a radon measurement, such as open windows, unusual ventilation, nearby fans, moisture, or detector mishandling. Recognizing interference helps the tester decide whether results are valid or need repeating.

The systematic change in indoor radon concentration across the year, usually higher in winter when heating and closed windows reduce ventilation. It is the main reason long-term tests better represent annual average exposure.

The lowest concentration an instrument or method can reliably distinguish from background, often stated as a lower limit of detection. Results near or below it carry high relative uncertainty and should be interpreted cautiously.

Actions taken to reduce indoor radon concentrations, such as sub-slab depressurization, sealing, or ventilation changes. A measurement professional may recommend it but typically does not perform the mitigation work itself.

A radon measurement performed after a mitigation system is installed and operating, to confirm that concentrations have fallen as intended. It is usually done under closed-house conditions after the system has run for at least 24 hours.