NRPP RMFT cheat sheet

Radon-222 is a noble gas produced by alpha decay of radium-226 in the uranium-238 decay chain; its half-life is 3.82 days, so measurement timing must respect ingrowth and decay equilibria.

Short-term tests run 2 to 90 days (commonly 2 to 7 days with closed-house conditions); long-term tests run more than 90 days and better represent annual average exposure.

Closed-house conditions: all exterior doors and windows closed, no fans or devices bringing outside air in, starting at least 12 hours before test start and lasting through the test; normal entry and exit is permitted.

Placement rules of thumb: lowest livable level, 20 inches (50 cm) above floor, at least 12 inches (30 cm) from exterior walls, 4 inches (10 cm) from other objects, and at least 3 feet (1 m) from windows, doors, and air vents.

EPA action level is 4 pCi/L (about 148 Bq/m3); the EPA recommends considering mitigation between 2 and 4 pCi/L. The WHO reference level is 100 Bq/m3.

Devices fall into two families: passive (activated charcoal, alpha track, electret ion chamber, charcoal liquid scintillation) and active/continuous (pump-driven or electronic monitors logging hourly data).

Duplicate (side-by-side) measurements and blank/spike quality-control samples are required at a defined percentage of placements to verify precision and detect field or lab errors.

Chain-of-custody: record device serial number, placement location, start and stop date/time, and closed-house confirmation; ship promptly to the lab within the device's holding time.

Deployment steps in order: review building and prior test history, select device locations, document closed-house conditions, place devices, record start date/time, retrieve on schedule, and complete chain-of-custody.

Do not test in kitchens, bathrooms, laundry rooms, closets, crawl spaces, or hallways; choose a frequently used room such as a family room or bedroom on the lowest livable level.

If a device cannot be placed on the lowest livable level, document why and place it in the next-best occupied space; slab-on-grade and basement rooms are preferred over upper floors.

Record a floor plan sketch with device locations, room names, and distances from walls and vents so the measurement is reproducible and defensible.

Avoid placing devices near heat sources, fireplaces, sumps, drains, or HVAC returns, since local air movement and moisture can bias results.

Test duration is chosen before deployment; do not shorten a scheduled long-term test because of an early high reading, and do not extend a short-term test to 'average out' an anomaly.

Occupant instructions: maintain closed-house conditions, do not tamper with the device, note any unusual events (storms, power outages, remodeling), and sign the receipt when the device is retrieved.

Post-mitigation verification testing uses the same placement and closed-house rules as the original test, performed no sooner than 24 hours after mitigation system operation begins.

Calibration: continuous monitors and electret readers require annual calibration traceable to a primary standard; passive devices are calibrated by lot through the manufacturer or laboratory.

Cross-check each active monitor against a reference device or a known radon chamber at least annually; record reference value, measured value, ratio, and pass/fail against the acceptance window.

Electret ion chamber voltage decay is converted to radon concentration using a manufacturer-supplied calibration factor and the exposure period; correct for background voltage loss.

Charcoal devices are sensitive to temperature and humidity; observe the manufacturer's exposure window (typically 2 to 7 days) and holding time before analysis.

Alpha-track detectors integrate exposure over months; they are unaffected by short-term humidity swings but must be returned by the stated exposure end date.

Quality control categories: duplicates, blanks, spikes, and cross-checks; each has a defined acceptance criterion, and out-of-tolerance results trigger an investigation, not automatic discard.

Maintain a device log: serial number, calibration date and due date, deployment history, and any repairs; a device past calibration due date cannot be deployed.

Field instrument checks include battery condition, pump flow verification for active samplers, and leak checks on sample lines before each use.

Report contents: client and property identification, test method and device type, device serial numbers, placement locations, test start and stop date/times, test duration, and measured concentration with units.

State whether closed-house conditions were confirmed and whether any deviations or unusual events occurred; deviations must be described, not hidden.

Report the result in pCi/L and, where required, Bq/m3; conversion is 1 pCi/L = 37 Bq/m3.

Interpretation: below 2 pCi/L is low; 2 to 4 pCi/L warrants consideration of mitigation; at or above 4 pCi/L mitigation is recommended.

Duplicate results are reported as the average of the pair when both are valid; if the pair disagrees beyond the acceptance criterion, report the discrepancy and recommend retest.

Invalid or compromised tests (broken closed-house conditions, device tampering, expired holding time) should be reported as invalid with the reason and a retest recommendation.

Confidentiality: results belong to the client; do not disclose to third parties such as buyers, sellers, or real estate agents without written client authorization.

Retain records (chain-of-custody, placement data, QC results, calibration records) for the period required by the certification body or state program, commonly at least two years.

Measurement error sources: device placement error, failure to maintain closed-house conditions, HVAC operation, barometric pressure swings, humidity, and temperature extremes.

Counting statistics: a result near the detection limit has large relative uncertainty; report the uncertainty or minimum detectable concentration alongside low values.

Avoid reporting a single short-term result as an annual average; short-term tests indicate potential, while long-term tests estimate typical exposure.

Radon entry routes: cracks in slab and foundation walls, slab-to-wall joints, sump pits, floor drains, and hollow-block foundations; the driving forces are stack effect, pressure differentials, and diffusion.

Mitigation basics technicians should recognize: sub-slab depressurization with a continuously operating fan, sealed penetrations, and a routed vent stack terminating above the roofline.

Post-mitigation radon levels should be verified by an independent test; a common goal is below 2 pCi/L, and the action level remains 4 pCi/L.

If a mitigation system is present, note it in the report, verify the fan is operating and the manometer shows expected pressure, and do not disable the system during testing.

Elevated readings in one room but not another usually indicate a local entry route or air-movement effect; investigate before concluding the building is uniformly high.

Certification programs (for example state radon programs and national credentialing bodies) require initial training, an exam, and continuing education; verify the specific jurisdiction's requirements.

Technicians work under the measurement provider's quality assurance plan; follow the written QA/QC plan for device handling, duplicates, blanks, and spikes.

Conflict of interest: a measurement technician should not also perform mitigation on the same property without disclosure, since results could influence the mitigation decision.

Safety: treat radon as a health hazard but not an acute exposure hazard; standard hygiene and safe ladder/confined-space practices matter more during field work.

Documentation must be contemporaneous; record times and observations as they occur rather than reconstructing them later.

Do not represent yourself as an official government inspector or claim government affiliation; state your certification accurately.

Continuing education and device calibration records are auditable; keep them current and available for the certifying body.

If a client asks for legal or medical advice about radon exposure, refer them to a qualified professional rather than interpreting risk yourself.