# Radon Glossary

- **URL:** https://airsenseenvironmental.com/radon-glossary/
- **Published:** 2026-10-04

This glossary explains common radon testing and mitigation terms in plain language. For concise machine-readable access, see the Markdown glossary. Radon A naturally occurring radioactive gas produced by the decay of uranium in soil, rock, and water. Radon is invisible, odorless, and tasteless, so testing is the only way to know a building's level. pCi/L Picocuries per liter, the unit commonly used to report radon concentration in air in the United States. Learn more in our guide to radon levels and pCi/L. EPA action level The U.S. EPA recommends fixing a home when the radon result is 4.0 pCi/L or higher and advises considering action between 2.0 and 4.0 pCi/L. Short-term radon test A test that typically lasts from 2 to 90 days. Many real-estate and diagnostic tests use a shorter closed-house measurement period. See short-term versus long-term testing. Continuous radon monitor An electronic instrument that records radon readings over time and can help identify unusual test conditions or hourly changes. Active soil depressurization A mitigation method that uses a continuously operating fan and sealed piping to draw radon-containing soil gas from beneath a building and exhaust it safely outdoors. Sub-slab depressurization A type of active soil depressurization in which suction is created beneath a concrete slab. See our detailed sub-slab depressurization guide. Sub-membrane depressurization A mitigation method for crawl spaces that uses a sealed membrane over exposed soil with suction beneath the membrane. Suction point The location where mitigation piping connects to the space beneath a slab or membrane so a fan can draw out soil gas. Pressure field extension The reach of negative pressure beneath a slab from a suction point. Diagnostic testing helps determine whether the proposed system can influence the required foundation area. Manometer A small pressure indicator installed on a mitigation system. It shows whether the fan is creating suction; it does not measure the radon level. See how to read a radon manometer. Radon fan A continuously rated fan designed to move soil gas through mitigation piping. Fan selection depends on foundation conditions and diagnostic results. Follow-up radon test A radon measurement performed after mitigation to measure the resulting concentration. Air Sense recommends arranging this test separately and confirming the provider, timing, and price in the written estimate; it is not automatically included with installation. Closed-house conditions Test conditions that limit outside-air exchange so a short-term result is meaningful. Exterior doors and windows stay closed except for normal entry and exit, subject to the applicable protocol. Service area A geographic area where a company performs work. A service area does not by itself represent a staffed physical office. Primary references U.S. EPA radon program U.S. EPA Consumer's Guide to Radon Reduction Illinois radon program Missouri Department of Health and Senior Services radon guidance These definitions are general information, not property-specific, medical, legal, regulatory, or contractual advice. Have a term you want explained? Contact Air Sense Environmental.