NRSB RMT flashcards

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

Radon-222 half-life

3.82 days. Because the gas decays quickly, a measurement reflects only the exposure period, and short-term tests must be deployed and retrieved on a tightly controlled schedule.

Uranium-238 decay chain

Radon-222 forms from radium-226 in the U-238 series. Its short-lived progeny (polonium-218, lead-214, bismuth-214, polonium-214) produce the alpha and gamma emissions most detectors count.

pCi/L to Bq/m3

Multiply picocuries per liter by 37 to obtain becquerels per cubic meter. The EPA action level of 4 pCi/L equals roughly 148 Bq/m3, the reference value used in many other countries.

Working level definition

One WL is any mixture of short-lived radon progeny in one liter of air releasing 1.3 x 10^5 MeV of potential alpha energy. One WL corresponds to about 200 pCi/L of radon at 50 percent equilibrium.

Equilibrium ratio F

The ratio of actual potential alpha energy concentration to the value at full secular equilibrium. Values in homes typically fall between 0.3 and 0.7, so progeny-based detectors must apply this factor.

Charcoal adsorption canister

A short-term passive device exposed 48 to 96 hours, then counted by gamma spectroscopy for lead-214 and bismuth-214. Humidity and temperature during exposure can bias the uptake of radon.

Alpha-track detector

A long-term device using CR-39 or LR-115 film exposed 90 days to a year. Alpha particles from radon and deposited polonium-218 leave etchable tracks counted under a microscope; results integrate seasonal variation.

Electret ion chamber

A passive device whose charged electret loses voltage as radiation ionizes the chamber air. Voltage drop relates to exposure; usable for short-term and long-term tests, with humidity correction and annual calibration.

Continuous radon monitor

An active electronic instrument that samples air and counts alpha decays, storing hourly readings. It documents tampering and barometric trends, and requires annual calibration plus periodic cross-checks against a reference.

Lucas cell counting

A classic grab-sampling method: air is drawn into a zinc-sulfide-coated scintillation cell and counted for alpha activity. It gives a near-instantaneous gas reading but requires careful timing after sampling.

Closed-house conditions

External doors and windows stay closed 12 hours before and throughout a short-term test. Heating and cooling may run normally; exhaust fans and permanent vents are not operated except as required.

Device placement height

Short-term and long-term detectors are placed at least 20 inches (50 cm) above the floor, 4 inches (10 cm) from other objects, and 3 feet (0.9 m) from exterior doors, windows, and air registers.

Lowest livable level rule

Testing is performed in the lowest level of the home that is lived in, not the basement if it is unfinished and unused. If multiple locations qualify, one detector is placed in each.

Unsuitable test locations

Bathrooms, kitchens, laundry rooms, closets, crawl spaces, and hallways are not used for placement because of atypical moisture, ventilation, or occupancy patterns that distort results.

Duplicate measurements

At least 10 percent of measurement locations receive two devices side by side. The precision check verifies field reproducibility and exposes handling or analysis errors that calibration alone would miss.

Spike and blank tests

A spike is a device exposed to a known radon concentration; a blank is an unexposed device carried through handling and analysis. Both are run at least annually per device type.

Calibration traceability

Each detector type is calibrated against a standard traceable to a national metrology institute. Calibration establishes the efficiency factor used to convert counts into reported picocuries per liter.

Confirmatory testing

When a first short-term test is at or above 4 pCi/L, a second short-term test or a long-term test is performed before mitigation is designed, reducing the chance of acting on an anomalous reading.

Test result uncertainty

Every reported concentration carries an analytical uncertainty, often stated at one or two sigma. A result near 4 pCi/L with wide uncertainty may warrant a longer or duplicate measurement.

Barometric pressure effect

Falling pressure draws soil gas into a house and can raise indoor radon; rising pressure suppresses entry. Short-term results therefore depend on weather during exposure, and severe storms should be avoided.

Stack effect

Warm indoor air rising through the house creates slight negative pressure at the base, pulling soil gas through foundation cracks. The effect is strongest in winter, which is why seasonal timing matters.

Radon entry routes

Soil gas enters through foundation cracks, slab joints, sump pits, utility penetrations, and block-wall cavities. Diffusion and pressure-driven flow both contribute, with pressure-driven flow usually dominant.

Radon in water

Groundwater can carry dissolved radon that is released during showering and washing. Water testing is considered when a private well serves a home with elevated air radon, and mitigation uses aeration or granular activated carbon.

Post-mitigation verification

After a mitigation system is installed, a short-term test is run under closed-house conditions, typically no sooner than 24 hours after system start-up, to confirm the concentration has fallen below the action level.

Sub-slab depressurization

The most common mitigation method: a fan draws soil gas from beneath the slab and vents it above the roof, reversing the pressure gradient that drives radon into the building.

Radon resistant new construction

New homes can be built with a passive soil-gas collection layer, sealed penetrations, and a vent stack that can later accept a fan. Activation and testing confirm performance after occupancy.

Short-term test duration

Charcoal and electret short-term tests run from 2 to 90 days, most commonly 48 to 96 hours. Longer exposure improves precision but increases sensitivity to weather and occupant behavior.

Long-term test duration

Alpha-track and electret long-term tests run at least 90 days, preferably through a heating season. They better represent the annual average and are preferred for deciding whether mitigation is needed.

Detection limit

The lowest concentration a method can distinguish from background, often about 0.1 to 0.5 pCi/L for charcoal and alpha-track devices. Results below the limit are reported with that limit noted.

Chain of custody

Documentation tracking each device from deployment through shipping and analysis, including exposure start and stop times, location, and handler signatures. Gaps can invalidate a measurement.

Progeny versus gas measurement

Progeny-based methods infer radon gas from daughter activity and depend on the assumed equilibrium ratio. Direct gas methods, such as scintillation cells or ionization chambers, do not require that assumption.

Measurement professional role

A radon measurement professional deploys devices per protocol, maintains closed-house conditions, documents locations and times, and reports results with uncertainty; mitigation design and installation are separate services.