INFORMATION SERIES: Radon Gas

Radon is an odorless, colorless radioactive gas which in the soil. This condition is commonly caused by the is formed by the natural breakdown of uranium. Radon can be found in high concentrations in soils and rocks containing granite, shale, phosphate and uranium, or occasionally industrial waste, in almost any area. As it
is produced, it moves through the soil to the earth's surface where it can either safely dissipate in outdoor air or seep into a building through cracks and gaps in
its foundation or slab. It can also be introduced into the air within a building through the water supply, particularly from well systems, or from certain building materials.

is difficult to readily determine average annual radon levels in a particular building. The greatest potential for high radon concentrations exists when the air pressure within a house is less than that of the radon gas use of appliances and fans in a relatively airtight structure. Appliances requiring air for combustion or other purposes lower indoor air pressure. This action draws in the high pressure radon laden air into the house through ground level cracks and openings. The illustration highlights the many common entry points for radon.

MEASUREMENT LEVELS

The U.S. Environmental Protection Agency (EPA) has established 4 picocuries per liter (pCi/I) or .02 working levels (WL) as the maximum acceptable continuous exposure level for radon in a residence. This level is not considered a finite cut-of point, rather it is a guidance point to determine when remedial action is advisable. Measurements of 1-4pCi/I are typically found in many houses in certain areas. This is considered a low level, which generally does not require any significant remedial action, depending on the specific situation or occupant concern.

The HouseMaster Technical Staff has summarized some of the standard radon mitigation methods:

• Forced Ventilation - This method utilizes fans or other mechanical means to exchange the radon laden indoor air for outdoor air.

• Heat Recovery Ventilation - Through means of a heat exchanger, this method utilizes the hot (or cold) air being exhausted to heat (or cool) the radon free
  incoming outdoor air.

• Sub-Slab Suction - This method utilizes vertical piping through the slab to draw the radon laden air from below the structure to the outside.

• Block-Wall Ventilation - With this method, a solid horizontal duct is installed and sealed in place over the horizontal wall/floor joint (or gap) around the entire basement perimeter. The radon laden air is then
  mechanically vented to the exterior.

• Pressurization - This method involves sealing of the basement from the rest of the house and then delivering air from upper floors to the basement, thereby
  increasing the air pressure in the basement and keeping radon gas out

Research has shown that once trapped inside a closed structure, radon can accumulate to the point where a potential health hazard may exist. Actually it is the breakdown of radon into what is referred to as radon decay products (or radon daughters) that represents the greatest concern. These decay products become attached to airborne particles which can be inhaled and ultimately cause lung tissue damage. The concentration of radon in any particular structure is dependent on a number of variable factors such as soil composition, building construction, weather conditions, and even occupant lifestyle. Levels may vary from day to day, season to season. Consequently, it 

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