NRPP RMP cheat sheet

Radon-222 is a noble gas produced in the uranium-238 decay chain; its immediate parent is radium-226, and its half-life is 3.82 days.

Radon-222 decays by alpha emission to polonium-218; the short-lived progeny (Po-218, Pb-214, Bi-214, Po-214) deliver most of the inhaled radiation dose.

Activity is expressed in becquerels (1 Bq = 1 decay/s); the U.S. working unit is the picocurie (1 pCi = 0.037 Bq), so 1 pCi/L equals 37 Bq/m3.

Working Level (WL) describes progeny alpha energy: 1 WL = 1.3 x 10^5 MeV of potential alpha energy per liter of air, equal to 100 pCi/L of radon at 50% equilibrium.

Equilibrium ratio equals the measured progeny concentration divided by the radon concentration at secular equilibrium; it is typically 0.3 to 0.7 indoors.

Radon-220 (thoron) has a 55-second half-life and generally decays before reaching significant distance from its source; it is not the target of standard radon tests.

Alpha particles from radon progeny travel only a few centimeters in air and cannot penetrate intact skin or a sheet of paper; detection depends on proximity or electrostatic collection.

Because radon concentration varies hourly, daily, and seasonally, a short-term test estimates exposure but a long-term test (>90 days) better represents the annual average.

Secular equilibrium between radon and its progeny is reached after roughly 3 to 4 hours in a closed space (about 7 half-lives of the 3.82-day parent).

The dominant driving force for soil gas entry is the pressure differential (typically a few pascals) created by stack effect, HVAC operation, and exhaust fans; diffusion is secondary.

Stack effect strength increases with indoor-outdoor temperature difference and building height, so radon entry often peaks in heating season.

Principal entry routes are cracks in slabs and foundations, slab-to-wall joints, sumps, floor drains, utility penetrations, and exposed soil in crawl spaces.

Soil permeability, radium content of soil, soil moisture, and the depth of the source all influence how much radon can be supplied to a building.

A sub-slab depressurization system reverses the soil-to-building pressure gradient; the radon fan must discharge above the roof edge and away from openings.

Depressurization of a house (fans exhausting air, furnace/boiler combustion air, downwind negative pressure) increases soil gas infiltration.

Upper floors usually show lower radon than basements or lowest lived-in levels because soil gas is diluted as it moves upward.

Radon in well water releases gas during showering, laundry, and dishwashing; waterborne radon can add to airborne levels, especially in small homes with high-water-use patterns.

Opening windows or operating a whole-house fan during a test invalidates the closed-house condition required for short-term tests.

Charcoal canisters and liquid scintillation detectors are short-term passive devices typically exposed 2 to 7 days; they are sensitive to temperature, humidity, and moisture.

Alpha-track detectors use CR-39 or similar plastic and are deployed for 3 to 12 months; they integrate exposure and are the standard for long-term tests.

Electret ion chambers measure radon by voltage drop on a charged electret; the difference before and after exposure is proportional to integrated radon concentration.

Continuous radon monitors (CRM) record hourly values, allow tamper detection, and are used for real estate and post-mitigation verification.

Short-term test protocol: closed-house conditions for at least 12 hours before and throughout the test; devices placed in the lowest livable level, 20 inches to 6 feet above the floor, away from drafts and exterior walls.

The EPA action level is 4 pCi/L; a confirmatory short-term test is recommended when the first result is 4 pCi/L or higher, or a long-term test may be used.

For real estate transactions, the test should be conducted in the lowest level suitable for occupancy, and the seller and buyer should agree on device placement and closed-house conditions in writing.

Grab samples and continuous working-level monitors measure progeny rather than radon gas and require different calibration and interpretation.

Duplicate and blank devices are deployed with each test batch to verify precision and detect contamination or shipping exposure.

A QA program includes written procedures, trained personnel, calibration records, and a documented chain of custody for each device.

Spikes, blanks, duplicates, and cross-checks with a reference method are the core QC samples; at least 10% of devices or a specified minimum should be QC samples per batch.

Devices must be calibrated at a qualified chamber against a known radon concentration; calibration factors are applied when reporting results.

The measurement uncertainty should be reported with each result; results near the action level require consideration of that uncertainty before decisions.

Control charts of QC results detect drift, bias, and out-of-control conditions; corrective action is documented when a control limit is exceeded.

Proficiency testing (PT) programs, such as those administered by a state or EPA-recognized provider, verify laboratory performance against known concentrations.

Device exposure time, shipping time, and storage must be tracked because charcoal devices continue to adsorb radon and lose it by decay.

Records should be retained for the period required by the certification body or state program, typically several years, and must be available for audit.

The U.S. EPA action level is 4 pCi/L; EPA also recommends considering mitigation at 2 to 4 pCi/L because no level is entirely risk-free.

The EPA Radon Measurement and Mitigation proficiency programs, along with state licensure, define who may test or mitigate; requirements vary by state.

ANSI/AARST standards (e.g., MAMF for measurement, RMS-LS for mitigation, and the real estate testing standard) set procedural requirements for professionals.

The Safe Drinking Water Act and related rules address radon in community water systems; the proposed MCL is 4,000 pCi/L with an alternate maximum contaminant level of 300 pCi/L for systems with mitigation.

The Indoor Radon Abatement Act (1988) authorized EPA assistance to states for radon surveys, training, and public information.

Disclosure laws in many states require sellers to inform buyers of known radon results or to provide a radon disclosure statement.

Ethical practice requires reporting results accurately, avoiding conflicts of interest, not altering devices or data, and keeping client information confidential.

Mitigation professionals should not perform the test that determines whether their own mitigation work passed unless the standard permits an independent verification arrangement.

OSHA and EPA worker-protection guidance applies to occupational radon exposure in mines and certain workplaces, not to typical residential testing.

Reports should state the device type, exposure dates, test location, closed-house conditions, and the measured concentration with its uncertainty.

Explain that 4 pCi/L is the action level and that results between 2 and 4 pCi/L warrant consideration of mitigation and retesting.

Clarify that a short-term test is a snapshot and that a long-term test better estimates the annual average exposure.

Avoid promising a specific health outcome; describe risk in general terms and refer clients to their physician for medical questions.

For real estate transactions, provide results promptly and in writing to all parties identified in the agreement, and document any deviations from protocol.

When a result is elevated, recommend confirmatory testing or mitigation by a qualified professional and provide the applicable state or EPA resource.

Explain the meaning of duplicate and blank results and why the reported value may differ slightly from a single device reading.

Document and disclose any condition that may have affected the test (open windows, fans, device tampering) so the client can interpret the result correctly.