How Radon Systems Work
How a Radon Mitigation System Works
A radon system does not filter the air already inside the home. It changes the pressure relationship between the building and the soil so radon-laden soil gas is collected before it can enter the occupied space.
Most systems use active soil depressurization: a fan draws air from beneath a concrete slab or sealed crawl-space membrane and exhausts it outdoors. The design must create a reliable pressure field across the foundation areas being protected.
Request a Radon System EvaluationThe Basic Airflow Path
- 1
Radon forms in soil and rock
Natural uranium decay produces radon gas. The gas moves through soil and can enter foundations through cracks, joints, sumps, drains, penetrations, crawl spaces, and other openings.
- 2
The building draws soil gas inward
Warm indoor air, exhaust equipment, wind, and pressure differences can make the building act like a weak vacuum on the soil.
- 3
The system creates a stronger controlled vacuum
A suction point or collection network connects to the soil beneath the foundation. The fan creates negative pressure beneath the slab or membrane.
- 4
Soil gas moves into the radon pipe
The gas follows the collection path instead of entering the home.
- 5
The pipe exhausts outdoors
The system discharges where radon can dilute in outdoor air and is less likely to re-enter the building.
Four Common Residential Designs
Sub-Slab Depressurization
A core hole and suction pit or collection point are created beneath the slab. The installer evaluates whether one point communicates across the slab or whether foundation divisions require more.
Sub-Membrane Depressurization
A durable membrane covers crawl-space soil. Sealed collection piping beneath the membrane applies suction to the soil-gas zone.
Mixed-Foundation System
Basements, slabs, crawl spaces, additions, and multiple elevations may use several suction points or independent systems.
Passive-System Activation
A fan and monitoring are added to a usable existing stack. The existing collection, route, and discharge must be inspected before activation.
The Components and What They Do
Collection zone
Gravel, soil-gas mat, perforated pipe, suction pit, or crawl-space network allows gas to move toward the system.
Gas-control barrier
The slab or sealed crawl membrane separates occupied space from the soil-gas collection zone.
Vent piping
Radon-rated pipe carries soil gas through a supported, labeled route to the fan and discharge.
Fan
The fan is selected for the pressure and airflow required. A larger fan is not automatically better and can increase noise, energy use, conditioned-air loss, or moisture issues.
Pressure indicator
A manometer or similar device shows that the system is creating pressure, but it does not measure the radon level.
Alarm or monitoring
Colorado requirements include system monitoring so a loss of operation can be detected.
Discharge
The outlet is positioned to reduce re-entry and protect occupants, openings, and adjacent spaces.
Post-mitigation test
Testing is the proof that the system reduced the indoor concentration under the test conditions.
What Sealing Can and Cannot Do
Sealing accessible cracks, sumps, penetrations, and membrane edges helps the system maintain suction and reduces conditioned-air loss. It rarely works as the only mitigation method because a building has many small, changing soil-gas pathways.
How the Installer Knows the Design Is Working
- The fan and monitoring operate correctly
- The measured system pressure is consistent with the design
- Pressure-field extension or communication is evaluated as appropriate across foundation zones
- Piping, fan, electrical, discharge, membrane, and labels are inspected
- A post-mitigation radon test documents the indoor result
Frequently Asked Questions
Get a System Designed for Your Foundation
Drennen evaluates the building rather than using a one-design-fits-all system. We consider foundation zones, route, appearance, service access, pressure, airflow, moisture, electrical needs, testing, and long-term maintenance.
Request a Radon System EvaluationSystem details vary. This page is educational and does not replace an on-site design by a licensed Colorado Radon Mitigation Professional.
Drennen Custom Contracting | Serving Fort Collins and Northern Colorado | 970-482-9100 | [email protected]