# Radon and Indoor Air Glossary

## Action level

A concentration at which an agency recommends action. The U.S. EPA recommends fixing a home when the radon level is 4 picocuries per liter (pCi/L) or more and advises considering action between 2 and 4 pCi/L. Source: https://www.epa.gov/radon

## Closed-house conditions

Test conditions intended to limit unusual outdoor-air exchange during a short-term radon measurement. Follow the instructions supplied with the test and applicable professional protocol.

## Continuous radon monitor

An electronic instrument that records radon measurements across time. Professional devices can help identify test interference and changes during the measurement period.

## Crawl space encapsulation

A moisture-control approach that covers exposed crawl-space soil and seals selected surfaces with a durable vapor barrier. In a radon system, a suction layer may be installed beneath the membrane.

## IEMA

The Illinois Emergency Management Agency and Office of Homeland Security, the state organization associated with Illinois radon licensing and regulation. Source: https://iemaohs.illinois.gov/nrs/radon.html

## Manometer

A pressure indicator mounted on many radon system pipes. Uneven fluid levels indicate that the fan is creating pressure; a manometer does not measure the home's radon concentration.

## Mitigation

Work intended to reduce indoor radon concentration. Active soil depressurization is the most common approach for existing homes.

## NRPP

The National Radon Proficiency Program, a certification program for radon professionals. Source: https://nrpp.info/

## Picocuries per liter (pCi/L)

The unit commonly used in the United States to report radon concentration in air.

## Post-mitigation test

A radon test conducted after a mitigation system has been operating to measure the resulting indoor concentration. Air Sense Environmental recommends a follow-up test; whether testing is contracted separately should be confirmed in the written scope.

## Radon

A radioactive gas produced by the natural decay of uranium in soil, rock, and water. It is colorless and odorless and can enter buildings through foundation openings. Source: https://www.epa.gov/radon

## Service area

The geographic region in which a company performs work. A service area is not the same as a staffed office or physical business location.

## Soil depressurization

A mitigation method that uses a fan and piping to draw soil gas from beneath a slab or membrane and exhaust it outdoors before it enters occupied space.

## Suction point

The connection through which a radon system draws soil gas from beneath a slab, drain tile, sump cover, or crawl-space membrane.