InterNACHI Certified Radon Tester study plan

Explain the uranium-238 decay chain from radium-226 to radon-222 and its short-lived progeny, and state each step's half-life from memory

Distinguish radon-222 from radon-220 (thoron) and explain why only radon-222 is the primary indoor concern

Define the units used in the field (pCi/L, Bq/m3, WL, WLM) and convert between pCi/L and Bq/m3 without a calculator error

Summarize the epidemiologic basis linking residential radon to lung cancer, including the synergistic effect with smoking

List the EPA action level and the WHO reference level and explain what each number means operationally

Describe how soil gas radon concentration is governed by source strength, soil permeability, and moisture

Diagram the four principal entry routes (cracks in slab, slab penetrations, sump/crawlspace, water supply) and label driving forces on each

Explain pressure-driven entry (stack effect, HVAC imbalance, exhaust fans, wind) versus diffusion and rank their relative contribution

Predict how seasonal temperature swings, barometric pressure changes, and rain/snow cover alter indoor radon concentrations

Identify building-construction features (drain tile, hollow block walls, unsealed penetrations) that create preferential pathways

Characterize the main measurement methods (activated charcoal, alpha track, electret ion chamber, continuous radon monitor, charcoal liquid scintillation) by integration time, sensitivity, and interference susceptibility

Explain the difference between a screening measurement and a diagnostic or post-mitigation measurement and when each device type is appropriate

Describe CRM features including tamper detection, hourly logging, and motion sensors, and explain why the data trace matters

Apply placement rules: lowest livable level, closed-house preconditions, avoidance of drafts, exterior walls, and high humidity

Explain why short-term tests require duplicate or follow-up testing when results fall near the action level

State the closed-house conditions required before and during a short-term test (typically 12 hours before, with windows and doors closed except for normal entry and exit)

Explain how to instruct occupants and document compliance, including what to record when conditions cannot be verified

Sequence a complete test visit: pre-survey, device deployment, chain of custody, retrieval, and shipping to the lab

Identify conditions that invalidate a test (severe storms, continuous operation of exhaust fans, unsealed openings) and describe how to handle each

Describe the required documentation for a real-estate transaction test versus a diagnostic test

Interpret a lab report including device type, exposure period, result, and uncertainty, and identify when a result is statistically indistinguishable from the action level

Explain the difference between a single short-term result and the annual average, and when confirmatory testing is warranted

Draft a client-facing report section that states results in plain language without overstating certainty

Explain reporting obligations regarding elevated results, recommended follow-up, and referral to a certified mitigator

Describe how to handle a client who requests a specific result or asks you to alter placement or conditions

Explain the principle of sub-slab depressurization and the roles of the suction point, piping, and vent fan

Distinguish active from passive mitigation systems and identify when a system needs a monitor or indicator

Describe post-mitigation verification testing requirements, including timing after system activation and placement of the test device

List common mitigation failure modes (fan failure, blocked piping, backdrafting, sealing failure) and their diagnostic signatures

Summarize the professional standards and ethical duties that govern a tester's independence from mitigation work

Re-derive the health-effects and dose concepts that clients most often question, including the comparison of radon risk to other familiar risks

Re-explain entry dynamics for a slab-on-grade, crawlspace, and basement home in under two minutes each

Review the standards and certification requirements that govern testing practice and list the records a tester must retain

Practice responding to three difficult client scenarios (disputed result, pressure to skip closed-house conditions, request for mitigation advice) in writing

Complete two full-length timed practice exams and score each by domain

Re-study any domain scoring below 80 percent, prioritizing the two lowest

Recite the key numeric facts (action level, closed-house duration, decay half-lives, unit conversions) from memory without reference

Review every missed question and write a one-sentence rule for each to prevent repeat errors