Skip to content
RADON411

Resources

Radon glossary

Every radon term in plain words, each with a worked example in numbers.

32 terms. Type to search, or pick a letter.

A

  • Units and levels

    Action level

    Also: EPA action level, 4 pCi/L

    The action level is the radon level at which EPA recommends fixing a home: 4 pCi/L, which is 148 Bq/m³. It is a point to act at, not a line with safety on one side.

  • Radon in water

    Aeration

    Also: aeration system, radon aeration, water aeration

    Aeration is a treatment for radon in well water that uses air to take the radon out of the water as it enters the home, then vents the radon outdoors. EPA puts its typical reduction at 95 to 99 percent.

  • The science

    Alpha particle

    Also: alpha radiation, alpha emitter

    An alpha particle is a positively charged particle made of two protons and two neutrons, given off when some radioactive atoms decay. Radon-222 is an alpha emitter.

  • Testing

    Alpha track detector

    Also: alpha track, alpha-track detector, ATD

    An alpha track detector is a passive radon test device that holds a special plastic or film inside a filter-covered chamber. Alpha particles from radon and its progeny strike the plastic and leave marks, which a laboratory reads.

B

  • Units and levels

    Bq/m³

    Also: becquerels per cubic meter, becquerel, Bq/m3

    Bq/m³ stands for becquerels per cubic meter, the metric unit for radon in air. Most countries report radon in it; the United States uses pCi/L.

C

  • Testing

    Charcoal canister

    Also: charcoal test kit, activated charcoal detector, radon charcoal

    A charcoal canister is a passive short-term radon test device: a small container of activated charcoal that takes up radon from the room air, then is resealed and sent to a laboratory for analysis.

  • Testing

    Closed-building conditions

    Also: closed-house conditions, closed house conditions

    Closed-building conditions, also called closed-house conditions, mean keeping all windows closed, keeping doors closed except for normal entry and exit, and not operating fans or other machines that bring in air from outside while a short-term radon test runs.

  • Testing

    Continuous radon monitor

    Also: CRM, continuous monitor, active device

    A continuous radon monitor is an electronic test device that measures and records the radon in the air again and again through the test, instead of giving one total at the end. EPA classes it as an active device: it needs power to work.

D

  • The science

    Decay chain

    Also: decay series, uranium decay series

    A decay chain is the series of radioactive atoms that one unstable atom passes through on its way to a stable one. Radon is a step in the chain that starts with uranium-238 in rock and soil.

E

  • Maps and data

    EPA zone

    Also: EPA radon zone, radon zone, Zone 1, Zone 2, Zone 3

    An EPA zone is a rating from 1 to 3 that EPA assigns to every U.S. county describing how much radon potential is predicted in that area, not the radon level in any specific building.

G

  • Radon in water

    Granular activated carbon

    Also: GAC, GAC filter, carbon filter

    Granular activated carbon, GAC for short, is a filter material used to take radon out of well water where the water enters the home. EPA puts its typical reduction at 85 to 95 percent.

H

  • The science

    Half-life

    Also: radioactive half-life

    A half-life is the time it takes for half of the radioactive atoms in a sample to decay. Radon-222, radon's most stable form, has a half-life of about 3.8 days.

  • Fixing

    Heat recovery ventilator

    Also: HRV, air-to-air heat exchanger, heat recovery ventilation

    A heat recovery ventilator, or HRV, also called an air-to-air heat exchanger, increases ventilation by bringing in outdoor air while using the heated or cooled air being exhausted to warm or cool the incoming air. More ventilation helps reduce the radon level in a home.

L

  • Testing

    Long-term test

    Also: long-term radon test, long term test

    A long-term test is a radon test that stays in the home for more than 90 days. It is more likely than a short-term test to tell you the home's year-round average radon level.

  • Testing

    Lowest lived-in level

    Also: lowest level, lowest livable level, test placement

    The lowest lived-in level is the lowest floor of a home that people regularly use, and it is where EPA says to place a radon test: the basement if it is frequently used, otherwise the first floor.

M

  • Maps and data

    Median

    Also: median radon level, middle value

    The median is the middle value in a set of test results lined up from lowest to highest: half of the results are above it and half are below.

  • Fixing

    Mitigation

    Also: radon mitigation, radon reduction, remediation, abatement

    Mitigation is work done to a building to reduce its indoor radon level, primarily with a vent pipe and fan system.

N

  • Professionals

    NRPP

    Also: National Radon Proficiency Program

    NRPP is the National Radon Proficiency Program, one of the two national programs in the United States that certify radon measurement and mitigation professionals.

  • Professionals

    NRSB

    Also: National Radon Safety Board

    NRSB is the National Radon Safety Board, the other national program in the United States that certifies radon measurement and mitigation professionals.

P

  • Fixing

    Passive subslab suction

    Also: passive radon system, passive system, passive soil depressurization

    Passive subslab suction is a radon vent pipe that runs from under the slab up through the house and out through the roof, with no fan. EPA says it is usually part of the radon-resistant features installed in newly constructed homes.

  • Units and levels

    pCi/L

    Also: picocuries per liter, picocurie

    pCi/L stands for picocuries per liter of air. It is the unit a radon test result is reported in across the United States.

  • Testing

    Post-mitigation test

    Also: post-mitigation, retest after mitigation

    A post-mitigation test is a radon test taken after a mitigation system is installed, to confirm the system has brought the level down.

  • Testing

    Pre-mitigation test

    Also: pre-mitigation, pre-mitigation level

    A pre-mitigation test is a radon test taken before a mitigation system is installed. It sets the starting level the system has to bring down.

R

  • The science

    Radon progeny

    Also: radon decay products, radon daughters

    Radon progeny are the radioactive atoms with short half-lives that radon quickly decays into. Also called radon decay products or radon daughters, they are solid particles, not a gas.

  • Fixing

    Radon-resistant new construction

    Also: RRNC, radon-resistant features, radon-resistant construction

    Radon-resistant new construction, RRNC for short, is a set of features built into a new home to keep radon out and to make a later fix simple: a gas-permeable layer under the slab, plastic sheeting, sealing and caulking, a vent pipe, and a junction box for a fan.

  • Units and levels

    Reference level

    Also: WHO reference level, 100 Bq/m3

    A reference level is the national radon benchmark WHO asks each country to set for homes: 100 Bq/m³ as an annual average where possible, and never above 300 Bq/m³.

S

  • Testing

    Screening measurement

    Also: screening test, initial test, follow-up test

    A screening measurement is a single short-term test result, treated as an initial read rather than a final answer.

  • Testing

    Short-term test

    Also: short-term radon test, short term test

    A short-term test is a radon test that stays in the home from 2 to 90 days, depending on the device, and for a minimum of 48 hours. It is the quick first measurement.

  • The science

    Soil gas

    Also: soil air, soil gases

    Soil gas is the gas in the ground under and around a building: air that carries radon and other gases up from the soil. EPA names radon from soil gas as the main cause of radon problems in homes.

  • Fixing

    Soil suction

    Also: drain-tile suction, sump-hole suction, block-wall suction, soil depressurization

    Soil suction is EPA's name for the radon systems that draw radon from below a home and vent it outdoors through pipes. In a home with a basement or a slab-on-grade foundation there are four types: subslab suction, drain-tile suction, sump-hole suction and block-wall suction.

  • Fixing

    Sub-membrane depressurization

    Also: submembrane suction, SMD, crawlspace radon system

    Sub-membrane depressurization, which EPA calls submembrane suction, is the radon fix for a crawlspace: the earth floor is covered with a high-density plastic sheet, and a vent pipe and fan draw the radon from under the sheet and vent it outdoors.

  • Fixing

    Sub-slab depressurization

    Also: subslab suction, active subslab suction, SSD, active soil depressurization

    Sub-slab depressurization, which EPA also calls active subslab suction, is the most common and usually the most reliable way to lower radon: a pipe through the foundation slab and a fan draw radon from under the house and vent it outdoors.