NRPP RMFT key terms

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

The SI unit for radon activity concentration, equal to one decay per second in a cubic meter. One pCi/L equals about 37 Bq/m3.

A measure of the potential alpha energy from short-lived radon decay products in a liter of air, used mainly in occupational and mine settings rather than in homes.

An exposure unit equal to breathing air at one working level for about 170 hours, used to express cumulative radon progeny exposure for workers.

The radon concentration at which mitigation or further evaluation is recommended. In U.S. residential guidance it is 4 pCi/L, with consideration of action between 2 and 4 pCi/L.

A colorless, odorless radioactive gas produced by the decay of radium in soil and rock. It seeps into buildings and is the leading environmental cause of lung cancer among nonsmokers.

Short-lived radioactive solids such as polonium, lead, and bismuth that form when radon decays. They attach to dust and can deposit in the lungs, delivering most of the dose.

A radioactive metal found in soil and rock that decays into radon. Its concentration in surrounding material largely determines how much radon gas can be produced.

The time required for half of a radioactive substance to decay. Radon-222 has a half-life of about 3.8 days, which affects how long test devices must be exposed.

Air present in pore spaces between soil particles. Radon-laden soil gas enters buildings through cracks, sumps, and other openings driven by pressure differences.

The upward flow of indoor air caused by warm air rising and leaving through upper openings, which lowers indoor pressure and draws soil gas into the building.

The difference in air pressure between indoor and outdoor or sub-slab environments. Even small negative indoor pressures can pull radon-containing soil gas indoors.

Test conditions requiring exterior doors and windows to remain closed, typically for at least 12 hours before and throughout the test, to measure representative radon levels.

A radon measurement lasting from a few days to about 90 days, often using charcoal or electret devices. It provides a quick screening result that may need confirmation.

A radon measurement lasting more than 90 days, usually with an alpha track or electret device. It better reflects the year-round average because seasonal variation is averaged out.

A passive short-term device containing activated charcoal that adsorbs radon for a set exposure period, then is analyzed in a lab to estimate average concentration.

A passive device that uses a charged electret to collect ions produced by radon decay; the voltage drop is measured to calculate radon concentration over the exposure period.

A passive long-term device with a plastic film that records alpha particle tracks from radon decay. Tracks are counted after processing to determine average radon concentration.

An electronic device that samples air and reports radon concentration at intervals, often storing hourly data and recording conditions such as temperature and pressure.

Choosing device locations that represent breathing air, such as lowest livable levels, while avoiding bathrooms, kitchens, and areas near drafts, heat, or exterior walls.

The lowest floor of a building that is used regularly, such as a basement or ground floor. Radon testing is normally performed there because concentrations tend to be highest.

The planned duration during which a radon measurement device is exposed to indoor air. It must match the device's design and the test protocol to produce valid results.

Changes in indoor radon concentration across the year caused by weather, heating, and ventilation patterns. Long-term tests reduce its effect on reported averages.

Any condition or activity that can bias a radon measurement, such as opened windows, fans, fireplaces, or unusual weather, which must be documented and avoided.

Planned activities that ensure radon measurements meet defined standards, including calibration, duplicate and blank measurements, audits, and documented procedures.

Routine checks performed during measurement work, such as duplicates, blanks, and calibration verification, to detect errors and confirm that results are reliable.

Two devices deployed side by side at the same time and location. Comparing their results helps verify precision and detect handling or analysis problems.

A device handled and shipped like a field device but not exposed to the test environment. Its result checks for contamination or lab background during processing.

A device exposed to a known radon concentration, often in a chamber, to verify that a measurement system reports accurately across its working range.

The process of comparing an instrument's response to a known reference standard and adjusting or documenting its accuracy so reported concentrations are traceable.

Documentation tracking a measurement device from deployment through shipping and laboratory analysis, showing who handled it and when at each step.

Building techniques that reduce indoor radon entry or increase ventilation, such as sub-slab depressurization, sealing, or ventilation, applied when test results warrant action.

A common mitigation method that uses a fan and piping to draw soil gas from beneath the foundation and vent it outdoors, lowering pressure under the slab.

A radon measurement performed after mitigation is complete to confirm that concentrations have been reduced to acceptable levels and the system is working.

The construction of a building's base, such as basement, slab-on-grade, or crawlspace. It influences radon entry routes, testing strategy, and mitigation design.

An estimate of the likelihood that a building in a given area will have elevated radon, based on geology, soil, and building characteristics. It guides testing priorities.

The proportion of radon decay products that attach to airborne particles rather than remaining unattached. It affects where progeny deposit in the respiratory tract.

A radon test performed as part of a property transaction, which must follow strict placement, closure, and documentation requirements so results are defensible.