ResourcesGlossary: fixing
Sub-slab depressurization
Short answer
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.
What sub-slab depressurization means
EPA describes the mechanism: a radon vent fan connected to the suction pipes draws the radon gas from below the home and releases it into the outdoor air, while creating a negative pressure, or vacuum, beneath the slab.
Often, EPA says, only a single suction point is needed. The method works best if air can move easily in the material under the slab.
What the reduction leaves from 10 pCi/L
EPA puts the typical reduction of subslab suction at 50 to 99 percent. Each row applies a reduction in that range to a home that tests at 10
| Reduction | Level left, pCi/L | In Bq/m³ |
|---|---|---|
| 50 percent, the low end of EPA's range | 5 | 185 |
| 75 percent | 2.5 | 92.5 |
| 90 percent | 1 | 37 |
| 99 percent, the high end of EPA's range | 0.1 | 3.7 |
What it means for your home
A system needs two things to stay honest. EPA says a warning device must be installed to alert you if an active system stops working properly, and that the fan should never be turned off.
Check where the pipe ends. EPA says the exhaust must vent above the surface of the roof and at least 10 feet from windows, doors or other openings.
Where to go next
- Radon mitigation cost estimator. Price a subslab system for your foundation and your state.
- Radon mitigation systems: types and parts. The pipe, the fan, the gauge and how the types differ.