NRSB RMS flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Radon-222 half-life

Radon-222 has a half-life of 3.82 days and decays by alpha emission to polonium-218. This short half-life allows both short-term and long-term measurement strategies.

Working level definition

One working level is any combination of short-lived radon progeny in one liter of air that emits 1.3 × 10^5 MeV of alpha energy. It equals 100 pCi/L radon at 100% equilibrium.

Working level month

One WLM is exposure to one working level for 170 hours. It is the standard unit for cumulative radon progeny exposure and occupational dose assessment.

Equilibrium fraction F

The ratio of progeny activity concentration to parent radon activity concentration at a given time. Indoors F is typically 0.3 to 0.7 and depends on ventilation and aerosol conditions.

pCi/L to Bq/m3

One picocurie per liter equals 37 becquerels per cubic meter. To convert pCi/L to Bq/m³, multiply by 37; to convert Bq/m³ to pCi/L, divide by 37.

Pressure-driven soil gas entry

The dominant radon entry mechanism in most buildings. Indoor-outdoor pressure differences caused by stack effect, exhaust fans, and wind draw soil gas containing radon through foundation cracks and openings.

Diffusion entry

Radon moves from soil into buildings by molecular diffusion along a concentration gradient. It is generally a minor entry pathway compared with pressure-driven flow but matters in highly permeable soils.

Emanation

The release of radon atoms from solid grains into the surrounding pore space. Emanation coefficient depends on radium distribution, grain size, and moisture content of the material.

Secular equilibrium time

Short-lived radon progeny reach secular equilibrium with radon after about 3 to 4 hours in a closed environment. This timing is critical when using progeny measurement methods.

Alpha track detector

A passive radon measurement device using a plastic film that records alpha particle tracks. Tracks are chemically etched and counted to determine integrated radon concentration over deployment periods of one to twelve months.

Electret ion chamber

A passive radon monitor using a charged electret whose voltage decreases as radon decay products ionize the chamber air. Voltage drop is proportional to integrated radon concentration.

Charcoal canister

A short-term passive radon device using activated charcoal to adsorb radon. It is deployed for two to seven days and analyzed by gamma spectroscopy; results are sensitive to humidity and temperature.

Continuous radon monitor

An active electronic instrument that measures radon concentration at intervals and records a time series. It can detect diurnal variation, tampering, and abnormal events during short-term tests.

Closed-house test conditions

For short-term radon tests, all exterior doors and windows are kept closed and fans or other air-moving devices are not operated for at least 12 hours before and during the test, except for normal entry and exit.

Test placement height

Detectors are placed in the lowest lived-in level of the home, at least 20 inches above the floor, away from exterior walls, drafts, heat sources, and direct sunlight.

Duplicate and blank detectors

Quality control in radon measurement includes duplicate detectors at a rate of at least 10 percent and field blanks at least 5 percent to assess precision and contamination.

Spike measurement

A known radon concentration is added to a detector or chamber to verify accuracy. Spikes are part of quality assurance programs and help confirm calibration and analysis bias.

Radon in water measurement

Waterborne radon is measured by liquid scintillation counting or gamma spectroscopy after careful sample collection. It contributes to indoor radon through household water use, especially showers.

Radon in soil gas

Soil gas radon is sampled with probes inserted into the ground and analyzed for concentration and permeability. It informs sub-slab depressurization design and radon potential assessments.

Radon potential

An estimate of the indoor radon concentration likely in a building at a location, based on geology, soil gas radon, and building characteristics. It guides testing and mitigation decisions.

Short-term test duration

Short-term radon tests last from two to ninety days depending on the device. Charcoal canisters are typically two to seven days, while alpha track detectors can be deployed for months.

Long-term test duration

Long-term radon tests last more than ninety days, typically three to twelve months. They provide a more representative annual average because they capture seasonal variation.

Radon action level

The U.S. EPA recommends mitigation when a long-term test average is 4 pCi/L or higher. The World Health Organization recommends a reference level of 100 Bq/m³.

Radon measurement plan

A written document describing sampling design, device placement, chain of custody, quality control, and reporting for a radon measurement project. It ensures consistency and defensibility.

Chain of custody

A documented record tracking radon detectors from deployment through retrieval, shipping, and laboratory analysis. It preserves sample integrity and supports data defensibility.

Detector deployment log

A field record noting detector identification, location, placement height, start and end times, and environmental conditions. It supports quality assurance and data interpretation.

Radon entry through crawl spaces

Crawl spaces can act as collection plenums for soil gas. Radon can move from the crawl space into living areas through pressure-driven flow and openings in the floor.

Sub-slab depressurization

A mitigation technique that uses a fan and piping to create negative pressure beneath the slab, preventing soil gas from entering the building. It is the most common radon reduction method.

Radon progeny plate-out

The deposition of charged radon decay products onto surfaces such as walls and furniture. Plate-out reduces the airborne progeny concentration and lowers the equilibrium fraction.

Radon measurement uncertainty

The combined uncertainty from detector calibration, counting statistics, and environmental variation. It is reported with results and used to decide whether a result exceeds an action level.

Radon chamber calibration

Detectors are exposed to a known radon concentration in a controlled chamber to determine calibration factors. Chambers are traceable to national standards and are part of quality assurance.

Radon test interference

Events such as opening windows, operating exhaust fans, or unusual weather can bias short-term radon results. Monitors and field logs help identify interference during the test.