Radon mitigation is any process or system used to reduce radon concentrations in the breathing zones of occupied buildings. The goal of a radon mitigation system is to reduce the indoor radon levels to below the EPA action level of 4.0 pCi/L. A quality radon reduction (mitigation) system is often able to reduce the annual average radon level to below 2.0 pCi/L.
There are several methods used to mitigate or reduce radon levels in your home. Some methods prevent the entry of radon, while others reduce radon levels after it enters the home.
Prevent the entry of radon
Houses are generally categorized by their foundation design, basement, slab-on-grade or crawl space. The foundation determines the radon reduction system that will work best to prevent gases from entering your home. Some homes can have more than one foundation design, requiring a combination of systems be used.
There are four types of soil suction systems: sub-slab, drain tile, sub-membrane and block wall.
The active sub-slab suction (also called the sub-slab depressurization, or SSD) is the most common and usually the most reliable system because it draws radon-filled air from beneath the house and vents it outside.
Passive sub-slab suction in new construction relies on air currents instead of a fan to draw sealant radon up from below seal floor the house & wall cracks and is not as effective.
If a home uses drain tiles to direct water away from the foundation, suction on the drain tiles can help reduce radon levels.
In the drain tile suction system, caps are placed on the sump pump baskets. The pump continues to drain unwanted water.
Block wall suction systems are used in homes with hollow block foundations by using a system similar to the sub-slab suction, where radon is removed from the wall by depressurization
Crawl Space Ventilation
Ventilation can sometimes lower indoor radon levels in crawl spaces by reducing the home’s suction on the soil and by diluting the radon beneath the house. Passive ventilation is achieved by opening or installing vents. Active ventilation uses a fan to blow air through the crawl space. To be effective, ventilation is often used with sub-membrane depressurization, which covers the dirt of the crawl space floor with a plastic sheet. A pipe then draws the radon air from under the sheet to the outside.