Radon is a colorless, odorless radioactive gas that naturally occurs when uranium breaks down in rock, soil or water. The air in a home's interior is less pressurized than the ground outside, and this negative pressure situation creates a vacuum to draw radon inside the home. Basements typically have higher radon levels, followed by first floors.

Radon exposure is the second-leading cause of lung cancer next to smoking, and it is the primary cause of lung cancer among non-smokers. Both the EPA and the U.S. Surgeon General recommend testing, plus radon mitigation if high levels are found. A home needs to have less than four picocuries per liter of indoor air to be exempt from needing a radon mitigation system. Homeowners with levels between two and four picocuries per liter may also want to consider radon mitigation.

Modern radon mitigation technology can lower a home's levels to two picocuries per liter or below. The first step is a radon test run for a minimum of 48 hours. For a more accurate picture of radon levels over time, homeowners can run the test for months.

If radon levels are too high, the EPA recommends hiring a qualified radon mitigation contractor to install the system. Most state radon offices keep a list of approved radon mitigation contractors. There are several types of radon mitigation techniques available, depending on the type of foundation.

1. Radon mitigation for basement and slab foundations.

For these foundations, the most common and often most effective type of radon mitigation system is active sub-slab suction, also called sub-slab depressurization. One or more pipes are run through the slab to the crushed rocks or soil underneath. The radon mitigation installer may also insert the pipes into the rocks or soil from outside the home. The pipe has a radon vent fan that draws the gas outward to release it into the air outside.

Passive sub-slab suction is designed in the same way except that radon mitigation is accomplished through air pressure rather than vent fans. This type of system is usually designed into new homes since it is less effective as a radon mitigation system in existing homes. Some homes that have a sump pump can use sump-hole suction to reduce radon levels. Block-wall suction can be used in homes with hollow-block basement walls.

2. Radon mitigation for crawlspace foundations

Sub-membrane suction is the most effective radon mitigation method for crawlspaces. A plastic sheet is placed over the dirt floor of the crawl space. A vent pipe is then placed under the plastic sheet and run through an opening to the outdoors. A fan is used to vent radon from the pipe. In homes with lower initial radon levels, covering the crawlspace with plastic and running a vent fan may be sufficient for radon mitigation.

3. Other methods of radon mitigation

sealing any basement cracks will help in radon mitigation. Some homeowners use a fan to blow air from the main floor into the basement, increasing the pressure to keep out radon. A heat-recovery ventilator (HRV) also termed an air-to-air heat exchanger can also help in radon mitigation.

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Call 1-800-NO-RADON