NRPP RMS key terms

A unit of radon decay product concentration equal to any combination of short-lived radon progeny that releases 1.3 × 10^5 MeV of alpha energy per liter of air. Used as the basis for action levels.

A cumulative exposure unit representing exposure to one Working Level for 170 hours, roughly one occupational month. Used to express lifetime or annual occupational radon progeny exposure.

The common U.S. unit of radon gas concentration, meaning trillionths of a curie per liter of air. One picocurie equals 2.22 nuclear transformations per minute.

The SI unit of radon activity concentration, equal to one nuclear transformation per second in a cubic meter of air. One pCi/L equals 37 Bq/m³.

The radon concentration at which mitigation or further evaluation is recommended. In the U.S. the commonly cited level is 4 pCi/L for long-term occupied spaces.

The U.S. Environmental Protection Agency's recommended threshold of 4 pCi/L for indoor radon, above which mitigation is advised. It is a guidance level, not a mandatory federal standard.

A radon measurement conducted for a period of 2 to 90 days, typically using charcoal or electret devices. Used for screening and real-estate transactions but more subject to seasonal variation.

A radon measurement lasting more than 90 days, usually with alpha-track or electret devices. Provides a more representative annual average because it spans seasonal and weather variation.

Measurement conditions requiring exterior doors and windows kept closed, typically 12 hours before and throughout a short-term test, with normal heating or cooling operating. Prevents dilution by outdoor air.

The selection of measurement locations within a building, generally the lowest livable level and occupied rooms, away from exterior walls, drafts, and moisture sources. Placement strongly affects result validity.

The lowest floor of a building that is suitable for occupancy, such as a basement with finished living space or a slab-on-grade floor. Measurements are typically made here because radon concentrates at lower levels.

A passive radon measurement device using a plastic film that records alpha particle tracks from radon decay. Suitable for long-term tests and less affected by short-term fluctuations.

A passive radon device in which an electrically charged electret is discharged by ionizing radiation; the voltage drop indicates radon concentration. Can be used for short- or long-term measurements.

A passive short-term radon device in which activated charcoal adsorbs radon gas for later laboratory counting. Typically deployed for 2 to 7 days and sensitive to temperature and humidity.

An electronic instrument that measures radon concentration at intervals, such as hourly, and stores time-series data. Useful for detecting tampering and short-term variation during real-estate tests.

The ratio of actual radon decay product concentration to the concentration expected at full equilibrium with the parent radon gas. Values below 1.0 indicate incomplete equilibrium, common indoors.

Short-lived radioactive daughters of radon, such as polonium-218 and polonium-214, that emit alpha particles. They are the primary source of radiation dose to lung tissue.

A written document describing measurement objectives, methods, calibration, and quality control procedures for a radon measurement project. Required for many regulated or contract measurement programs.

A quality control check in which a device is exposed to a known radon concentration and its reported result is compared with the known value. Evaluates measurement bias and accuracy.

Two devices deployed side by side at the same location for the same period to assess precision. Differences between results reveal random error in the measurement process.

The effect of non-radon factors, such as humidity, temperature, or other gases, on a detector's response. Addressed through calibration and device-specific correction factors.

Documentation tracking a measurement device from deployment through retrieval and laboratory analysis, recording who handled it and when. Prevents sample mix-ups and supports result defensibility.

Air contained in pore spaces of soil and rock, which can carry radon from uranium-bearing material toward a building foundation. Its radon concentration and permeability drive entry potential.

The ease with which gas flows through soil, governed by grain size, compaction, and moisture. Higher permeability allows more radon-laden soil gas to move toward and into a building.

The spatial reach of the sub-slab pressure difference created by a mitigation fan. Adequate PFE means the vacuum extends under the slab to intercept soil gas before it enters.

A mitigation technique that uses a fan and piping to draw soil gas from beneath a slab and vent it outdoors, lowering pressure below the slab relative to the building interior.

An engineered set of components, including suction points, piping, and a fan, designed to reduce indoor radon concentrations. Must be designed, installed, and labeled per applicable standards.

The location where a mitigation system extracts soil gas, such as a pit beneath a slab or a sump. Its placement and sealing determine how effectively vacuum spreads under the slab.

A pit at the low point of a basement floor that collects water. It can serve as a suction point if properly sealed, or act as a radon entry route if left open.

Closing openings such as cracks, joints, sumps, and penetrations to limit soil gas entry. Sealing alone rarely reduces radon enough but improves the performance of depressurization systems.

A diagnostic test that measures how easily air moves through sub-slab material, often by applying suction and observing pressure or flow. Informs suction point placement and fan sizing.

A pressure gauge, often a U-tube or digital device, used to verify that a mitigation system is developing vacuum and that the fan is operating. Provides a visual system-performance indicator.

A durable notice placed on a mitigation system identifying the installer, installation date, and service contact, and warning occupants not to disable the system. Required by mitigation standards.

The blower that draws soil gas through the mitigation piping and discharges it above the roof. Must be rated for the application and located to avoid discharging near windows or air intakes.

The outdoor location where a mitigation system vents soil gas, typically above the roof line and away from openings. Proper placement prevents re-entry of radon into the building.

A membrane or barrier installed over exposed soil in crawl spaces or beneath slabs to restrict soil gas movement into the building. Must be sealed at edges and penetrations to be effective.

A mitigation approach that draws air from a sealed crawl space and vents it outdoors, preventing soil gas from moving into the living space above. Requires a sealed barrier over the soil.

A radon measurement performed after a mitigation system is installed to confirm the reduction meets the target. Should follow the same closed-house and placement protocols as the original test.