Radon glossary

Action level

The radon level at which the Health Department and EPA recommend reducing radon in your home: 4.0 pCi/L. They also encourage action to get below 2.0 pCi/L.⁠¹ More

Active soil depressurization (ASD)

The usual radon fix: a vent pipe and a fan that draw radon from under the house. The Health Department estimates $1,500 to $2,500 installed.⁠^2,3 More

Aeration

A radon in water treatment: a fan mixes your water with air inside a tank or well casing, then vents the air and radon outdoors. Estimated at around $7,000.⁠³ More

Advisory level (water)

Vermont’s advisory level for radon in drinking water is 4,000 pCi/L. At or above it, the Health Department says to take action to reduce radon in your home.⁠⁴ More

Bq/m³ (becquerels per cubic meter)

The unit many other countries and some monitors use. 37 Bq/m³ is equal to 1 pCi/L.⁠⁵ More

Closed-house conditions

For a short-term test, close your windows and outside doors and keep them closed as much as possible during the test; for a 2- or 3-day test, close them at least 12 hours before you begin.⁠⁶ More

Consumer digital radon monitor

A home device that measures radon continuously while it has power. CRCPD says to verify its results with an approved test and never to use one in a real estate transaction.⁠^7,8 More

Granular activated carbon (GAC)

A charcoal filter that removes radon from water. The Health Department discourages GAC for radon because radon collected on the filter can pose a radiological hazard.⁠³ More

HRV or ERV (heat or energy recovery ventilator)

Exhausts air from the home and replaces it with fresh outdoor air. Best for moderate radon levels or to supplement an ASD system; around $7,000 when no additional ducting or electrical work is needed.⁠³ More

Long-term test

A test left in place for 3 to 12 months, ideally including a heating season: the Health Department’s recommended way to learn your home’s typical level. The Lab’s kit is $25.⁠^1,9 More

NRPP and NRSB

The National Radon Proficiency Program and the National Radon Safety Board: the two national directories of certified radon professionals the Health Department points to.⁠¹ More

pCi/L (picocuries per liter)

The unit for radon in air in the United States: picocuries per liter of air.⁠⁶ More

Radon-resistant new construction

Building features that keep radon out: a gas-permeable layer under the slab, plastic sheeting, sealed floor openings, a vent pipe and an electrical junction box. The Health Department puts the cost at $250 to $750.⁠¹⁰ More

Short-term test

A quick test for a real estate transaction or other times you need an answer fast. The Health Department says to use two short-term kits placed side by side.⁠^1,11 More

Working Level (WL)

A unit some professional reports use. The EPA recommends fixing your home if the result is 0.016 WL or higher.⁠¹² More

Last reviewed October 17, 2026 · How we source facts