Radon Mitigation
Radon Mitigation

As airborne radon in buildings constitutes a major health risk worldwide, measures to reduce radon levels represent an important consideration for homes, schools, and workplaces. Simple ways to reduce radon substantially reduce associated health risks. Since radon primarily enters buildings from the floor, two basic ways to reduce radon exist, preventing it from seeping into the building or extracting it from the building once it has entered. The most appropriate mitigation technique depends on the particular case for each building and owners may choose from among various methods or combinations of methods based on either or both of these concepts.

Preventative Techniques

The simplest method to reduce radon levels is to thoroughly seal gaps, cracks, and joints under floors with a durable sealant. However, in order to be effective, all these spaces must be sealed. Gaps left unsealed still allow radon seepage and limit the effectiveness of this method. Another method, positive pressurization, marginally increases air pressure within a building using a special attic fan to blow air into the rest of the building. The difference in air pressure between the building's interior and exterior expels air to the outside through the gaps and the radon is forced out of the building with it. These fans do not require complicated installation nor modifications to building structure and also decrease condensation in a building, resulting in other benefits such as mildew reduction.

On the other hand, operating these systems is more expensive than active sumps (explained below) and drafty buildings may require additional means to attain a sufficient amount of pressure. Therefore, positive pressurization depends highly on a building's impermeability to outside air intrusion.

Extractive Techniques

Also known as soil suction, one of the most common remediation methods utilizes bucket-sized cavities in the floor known as sumps. Cavities are connected to pipe networks leading to the outside. Sumps act to change pressure differentials between building's interiors and exteriors by decreasing pressure in the exterior. An active sump utilizes a fan to draw the air beneath a building into the pipe system and then to the outside air. Passive sumps do not feature fans. They are less costly than active sumps and do not produce any noise, however they do not extract radon as effectively as active sumps. Thus, consumers may choose to employ passive sumps for buildings with radon levels that fall below dangerous levels and use active sumps for buildings with radon levels above those levels.

Many systems feature system monitors that give indications if the system does not operate properly. More than one sump may be needed for a single building as each one affects an area of about 250 square meters. Linking the piping system together with one central fan increases the system's efficiency. Some opt to increase ventilation within the building so that indoor air, heavily laden with radon, mixes with outside air containing lower radon levels. Air enters through vents in walls and windows. Also, this method does not require heavy or frequent maintenance.

Consumers should note that increasing ventilation this way is more effective when done on the ground floor, as ventilation increases in upper floors may cause air to rise through the building and become concentrated on the upper floors. Another option is to increase ventilation under a building. This method may employ two means, vents or "airbricks" located under a building's ground floor. Airbricks may be made of clay or plastic, the latter offering greater surface area. When installing airbricks, you should remember that their positioning influences their ability to effectively ventilate air. The number of sumps needed depends on the layout of the building, the floor area and the initial radon concentrations present. As a general rule, a single sump is effective over a surface area of 250 square meters. Several sumps can be linked together and served by the one fan.


Costs vary among systems and the total cost to the building owner depends on the particular radon level and the methods chosen to reduce the level. A professionally installed system may range from $800 to $2,500. For that reason, some building owners prefer to try different methods, starting with the simplest and most inexpensive and then choosing successively more complex, expensive methods until reaching the method that effectively removes radon at the lowest possible price. Some building owners also choose to apply the methods themselves first, contacting professionals when their efforts prove ineffective. Those who chose to reduce radon themselves should contact their state radon agency.

Nevertheless, professional-level skills are required to effectively reduce radon, especially when at dangerous levels. Each state certifies professionals in radon reduction systems and the state radon agency may provide a list of certified professionals. Also, the Environmental Protection Agency offers information on radon reduction. Many experts recommend periodic building retesting.


Radon poses a serious health risk everywhere in the world. Due to this danger, many different methods for reducing radon levels are available. Building owners may reduce radon by preventing it from entering buildings or by extracting it from buildings once it has entered. Methods include sealing cracks, ventilation, and using sumps. These methods vary in effectiveness, cost, and complexity. The appropriate measure or combination of measures also depends on a particular building's radon level. Building owners should weigh their choices of method based on all of these factors.