InterNACHI Certified Radon Tester

Radon-222 is a naturally occurring radioactive gas. From which parent radionuclide in the U-238 decay series does Rn-222 directly originate?

• AThorium-230
• BRadium-226
• CPolonium-218
• DUranium-235

What is the approximate half-life of Radon-222?

• A3.82 hours
• B3.82 days
• C3.82 minutes
• D3.82 years

Rn-222 decays by which type of radioactive emission?

• ABeta-minus emission
• BAlpha emission
• CGamma-only emission
• DPositron emission

Which of the following Rn-222 progeny are the principal alpha-emitters responsible for the lung dose from radon inhalation?

• APb-214 and Bi-214
• BPo-218 and Po-214
• CPb-210 and Po-210
• DRa-226 and Th-230

In the Rn-222 decay chain, what is the approximate half-life of Polonium-218 (Po-218)?

• A3.1 minutes
• B27 minutes
• C20 minutes
• D164 microseconds

Which Rn-222 progeny has the shortest half-life of approximately 164 microseconds?

• APolonium-218
• BLead-214
• CBismuth-214
• DPolonium-214

What is the standard unit of measure for indoor radon concentration in the United States?

• ABecquerels per cubic meter (Bq/m³)
• BWorking levels (WL) only
• CPicocuries per liter of air (pCi/L)
• DSieverts per hour (Sv/h)

Approximately how many Becquerels per cubic meter (Bq/m³) equal 1 picocurie per liter (pCi/L) of radon?

• A3.7 Bq/m³
• B37 Bq/m³
• C0.37 Bq/m³
• D370 Bq/m³

A 'working level' (WL) of radon progeny is defined as any combination of short-lived radon progeny in 1 liter of air that releases what amount of alpha-particle energy on decay?

• A1.0 × 10⁻⁵ MeV
• B1.3 × 10⁵ MeV
• C100 µCi
• D10 mSv

Radon gas itself is best described as:

• AA reactive, colored gas with a distinct odor
• BA colorless, odorless, tasteless noble gas
• CA liquid at room temperature
• DA magnetically attracted vapor

Which group on the periodic table includes radon, and what does this imply about its chemical behavior?

• AAlkali metals — highly reactive with water
• BHalogens — strong oxidizers
• CNoble gases — chemically inert under normal conditions
• DTransition metals — variable oxidation states

Compared with air, what is radon's relative density?

• AAbout the same as air
• BAbout one-tenth as dense as air
• CAbout 7–8 times denser than air
• DAbout 100 times denser than air

Once Rn-222 decays inside a home, the short-lived progeny tend to:

• ARemain as free gas atoms suspended uniformly in air
• BAttach to airborne particles and surfaces (plate-out)
• CDecay back into uranium
• DMigrate outdoors immediately

Thoron (Rn-220) is sometimes encountered indoors. Which statement about thoron is correct?

• AThoron has a half-life of about 3.82 days, similar to Rn-222
• BThoron has a half-life of about 55.6 seconds and is part of the Th-232 decay series
• CThoron is the same isotope as Rn-222 with a different name
• DThoron is a chemically active form of radon

Which of the following best describes 'secular equilibrium' as it relates to radon and its progeny?

• AA condition in which progeny activities equal the parent activity because the parent's ha…
• BA state in which all isotopes have the same half-life
• CA condition in which radon ceases to decay
• DA laboratory phenomenon that does not occur in homes

Most indoor radon enters a home from which source?

• ABuilding materials such as drywall
• BHousehold water from municipal supply
• CSoil gas migrating through foundation openings
• DOutdoor ambient air

What is the U.S. EPA action level for indoor radon in homes?

• A2 pCi/L
• B4 pCi/L
• C10 pCi/L
• D0.4 pCi/L

What is the World Health Organization (WHO) reference level for indoor radon?

• A100 Bq/m³ (≈2.7 pCi/L)
• B200 Bq/m³ (≈5.4 pCi/L)
• C400 Bq/m³ (≈10.8 pCi/L)
• D50 Bq/m³ (≈1.4 pCi/L)

Radon is recognized by the EPA as which of the following in the U.S.?

• AThe leading cause of lung cancer overall
• BThe second-leading cause of lung cancer overall and the leading cause among non-smokers
• CAn asthma trigger, not a carcinogen
• DA benign indoor air pollutant with no established cancer risk

How does smoking interact with radon exposure with respect to lung-cancer risk?

• ASmoking has no interaction with radon
• BSmoking and radon exposure act synergistically, multiplying lung-cancer risk
• CSmoking eliminates the risk from radon
• DRadon protects smokers from lung cancer

The EPA estimates approximately how many lung-cancer deaths per year in the United States are attributable to radon?

• AAbout 2,100
• BAbout 21,000
• CAbout 210,000
• DAbout 210

EPA guidance for homes with radon levels between 2 pCi/L and 4 pCi/L recommends:

• ANo action is necessary
• BConsidering mitigation, because health risk persists below the action level
• CImmediate mandatory mitigation
• DDemolition of the building

The principal biological mechanism by which radon causes lung cancer is:

• ADirect radon gas dissolving in blood and damaging the liver
• BAlpha-particle ionization of bronchial epithelial cells from decay of inhaled radon proge…
• CGeneration of free radicals from chemical reaction of radon with oxygen
• DThermal injury to the alveoli

Which population subgroup is most affected by lifetime radon exposure?

• ASmokers and former smokers, due to synergistic risk
• BNewborn infants only
• CPeople over age 90 only
• DPeople with no genetic predisposition to cancer

Why does EPA emphasize that 'there is no safe level' of radon exposure?

• ABecause the dose-response relationship is linear without an identified threshold
• BBecause regulators prefer absolute language
• CBecause radon affects only children
• DBecause radon is a teratogen, not a carcinogen

Average outdoor ambient radon concentration in the United States is approximately:

• A0.4 pCi/L
• B4 pCi/L
• C10 pCi/L
• D0.04 pCi/L

Average indoor radon concentration in U.S. homes is approximately:

• A0.4 pCi/L
• B1.3 pCi/L
• C10 pCi/L
• D20 pCi/L

How does EPA characterize the lung-cancer risk to a non-smoker living for a lifetime at 4 pCi/L compared with other risks?

• ARoughly equivalent to the risk of dying in a car accident
• BRoughly equivalent to the risk from drinking eight glasses of water per day
• CMuch lower than the risk of food poisoning
• DNegligible compared to all other indoor exposures

Is there a federal requirement to test for radon in privately owned residential homes outside real estate transactions?

• AYes, the EPA mandates annual testing in every home
• BNo, federal testing is voluntary in private homes, though strongly recommended
• CYes, OSHA requires radon testing in private homes
• DYes, HUD requires monthly testing in all owner-occupied homes

Approximately what fraction of U.S. homes is estimated to have an indoor radon level at or above the 4 pCi/L EPA action level?

• AAbout 1 in 15
• BAbout 1 in 5
• CAbout 1 in 100
• DAbout 1 in 1,000

Which foundation type generally presents the highest risk of elevated indoor radon concentration when other factors are equal?

• ABasement foundations
• BPier-and-beam foundations with open ventilation on all sides
• CSlab-on-grade with no joints
• DDetached structures with no foundation

On which level of a home should a short-term radon test typically be placed for an EPA-compliant initial measurement in a non-real-estate setting?

• ALowest livable level (any level the occupants live in or could finish to live in)
• BHighest level of the home
• CAlways the attic, regardless of use
• DOutside on the porch

Which physical phenomenon most directly drives soil-gas radon into a home during cold weather?

• ABernoulli effect from outdoor winds
• BStack effect — warm interior air rising creates negative pressure at lower levels, pullin…
• CCapillary action through paint
• DRadioactive attraction between concrete and soil

An unbalanced HVAC return-air system that draws air from a crawlspace can:

• AEliminate radon by dilution
• BHave no effect on radon levels
• CIncrease indoor radon by depressurizing the home and pulling soil gas through the foundat…
• DConvert Rn-222 into stable lead instantly

Common soil-gas entry routes into homes include all of the following EXCEPT:

• ACracks in the basement floor slab
• BFoundation-wall floor joint (cove joint)
• CSealed double-pane windows on the second floor
• DSump pits and utility penetrations

When evaluating a home for radon testing, the presence of an existing active sub-slab depressurization (ASD) system means:

• ANo testing is necessary — the system guarantees safe levels
• BThe tester should document the system, verify it is operating, and follow protocol for te…
• CThe tester must shut the system off for at least 24 hours before testing
• DThe home cannot be tested under any protocol

When evaluating a home with a partial basement and an attached slab-on-grade addition, the radon tester should:

• APlace a single detector in the highest level of the home
• BTest only the basement
• CTreat the basement and the slab-on-grade addition as separate measurement areas if used a…
• DTest only outside the home

Why is a vented crawlspace typically tested less reliably than an interior occupied space?

• ACrawlspaces are exempt from testing
• BOpen ventilation in a crawlspace produces high air exchange with outside air, so a crawls…
• CCrawlspaces always have higher radon than living spaces
• DDetectors will not function in crawlspaces

A short-term test placed in a kitchen near a stove and exhaust hood is problematic because:

• ACooking heat will increase radon concentration
• BDrafts, humidity, exhaust air, and use disturbance can bias the result and the location i…
• CThe cabinets shield the detector from gamma rays
• DStoves emit radon

EPA radon zones (Zone 1, Zone 2, Zone 3) on the radon map are used to:

• AReplace the need for testing because they guarantee accurate predictions
• BIndicate the predicted county-wide average indoor radon potential, helping prioritize bui…
• CMandate testing only in Zone 1
• DMark areas where radon is impossible

Before placing a short-term radon detector, the inspector should perform a site-specific visual evaluation that includes:

• AColor-matching the device to the wall
• BDocumenting foundation type, HVAC configuration, existing mitigation systems, weather, an…
• CAsking the occupant to sign a non-disclosure agreement
• DConfirming the home is unfurnished

When weather forecast warns of severe storms or hurricane-force winds during the planned deployment window, the appropriate action is to:

• AProceed regardless of weather
• BPostpone the test until stable weather conditions can be maintained, because severe storm…
• CSwitch from a CRM to a charcoal canister to compensate
• DAdd a second detector outdoors to average out the storm effect

Of these short-term passive devices, which one analyzes the integrated radon exposure by tracking how alpha particles damage a polycarbonate film?

• AActivated charcoal canister
• BAlpha-track detector
• CElectret ion chamber (EIC)
• DContinuous radon monitor (CRM)

An activated-charcoal radon test canister works on which detection principle?

• ADirect alpha-particle counting in real time
• BAdsorption of radon onto activated carbon, followed by laboratory gamma counting of Pb-21…
• CVoltage drop on an electret
• DVisual color change of a chemical reagent

Because charcoal canisters continually adsorb and desorb radon, a charcoal-canister result tends to be most weighted toward:

• ARadon present at the very beginning of the test
• BRadon present near the end of the test, with diminishing weight on earlier radon
• CAn exact unweighted integration of the entire deployment
• DOutdoor radon only

An electret ion chamber (EIC) measures radon by:

• ACounting alpha particles via a scintillation cell
• BRecording the voltage drop on an electrostatically charged disk caused by ionization from…
• CAdsorbing radon onto activated carbon and gamma counting
• DEtching a polycarbonate film

What is the principal advantage of using a continuous radon monitor (CRM) over passive devices for a real-estate transaction test?

• ACRMs are cheaper than passive devices
• BCRMs produce hourly readings that reveal tampering and closed-house violations and provid…
• CCRMs do not need calibration
• DCRMs are immune to weather influence