What are VOC’s?

VOC’s (volatile organic compounds) are typically derived from solvents, dry cleaning fluids, fuels, and by-products of chlorination, and may include chemicals such as carbon tetrachloride, tetrachloroethylene (a common solvent used in the dry cleaning industry, also known as "Perc" or PCE), trichloroethylene (a common solvent used for cleaning and degreasing, also known as TCE), methytlene chloride, benzene, and methyl tert-butyl ether (MTBE). Common sources include existing or discontinued underground storage tanks, dry cleaning operations, gas stations, and industrial processes.

Petroleum products and solvents are common volatile chemicals that can cause vapor intrusion. Gasoline, diesel fuel, and home heating oil are examples of petroleum products. Odors are frequently associated with petroleum spills or leaks. However, odors are not usually associated with solvent leaks or spills unless large amounts are released.


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Vapor Intrusion occurs when negative air pressure inside a home or building draws volatile organic compound (VOC) vapors up into the structure from underlying soil and water. These chemicals can sometimes travel underground from one property to another, and then enter through drains, cracks, crawlspaces, control joints, sumps, and utility penetrations, creating a potential health risk for occupants who inhale them.

Health Risk

Health risks include cancer, organ toxicity, or reproductive effects. No concentration of these chemicals may be considered healthy. Gases, such as methane from landfills, also present potential explosive hazards, requiring special treatment.

Low levels of volatile chemicals are commonly found in homes and businesses. Vapor intrusion can add to these types of chemicals, but typically at very low levels. When volatile chemical levels are high enough, people might temporarily experience headaches, nausea, and/or eye and respiratory irritation. These symptoms usually go away when the person moves into fresh air. If people breathe low levels of these chemicals for many years, there may be a health risk. Government agencies may take steps to reduce even low levels of volatile chemicals in order to be cautious and protective of people’s health.

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Vapor Mitigation Systems

Cascade Radon’s engineering techniques used in radon mitigation translate perfectly to resolving VOC concerns. Sub-soil and sub-membrane depressurization are the most common and effective means of reducing soil-borne VOC contamination, creating negative pressure in the soil beneath a building with a fan-driven vent system, which then exhausts the vapors to above the roofline. Installations may involve sealing of vapor entry points such as drains, sumps, cracks, and crawlspaces.

Cascade Radon is proud to be the Northwest’s only approved CETCO/Liquid Boot installation firm. This spray-applied, flexible vapor barrier provides a superior membrane surface to prevent VOC entry.

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Mitigation may also include changes or adjustments to existing HVAC systems.

VOC mitigation systems can also reduce the effects of other soil contaminates such as radon gas, and generally improve overall indoor air quality.

What other sources of volatile chemicals can make indoor air unhealthy?

Paints, paint strippers and thinners, glues, solvents, and air fresheners are examples of products that contain volatile chemicals that can affect indoor air quality. Dry cleaned clothing and cigarette smoke also contribute volatile chemicals to indoor air. Volatile chemicals occur in outdoor air when they are released from various industries and vehicles. Because buildings are not airtight, outdoor air can enter buildings and affect indoor air quality. These sources are taken into account when evaluating whether vapor intrusion is contributing to unhealthy indoor air.
Some steps you can take to prevent releases of volatile chemicals from products stored or used at your home or business:
• Don't buy more chemicals than you need at any one time.
• Store unused chemicals in appropriate containers in well-ventilated areas away from living spaces or work spaces.
• Place freshly dry cleaned clothes in a well-ventilated area.

What happens if vapor intrusion is a possible problem near my home or business?

When vapor intrusion is suspected, it should be investigated by the party responsible for the contamination. An investigation typically involves testing soil, groundwater, and soil gas (air trapped between soil particles). This testing helps to determine if volatile chemicals might pose an indoor air quality problem.

At many contaminated sites, volatile chemical levels are low and are not considered a problem. At times, the levels in soil, groundwater, or soil gas are high enough to cause concerns about indoor air quality in nearby homes or businesses. When a concern about indoor air quality exists, samples are often collected inside homes or businesses. The samples are needed to determine if the volatile chemical levels in buildings are making indoor air unhealthy and whether vapor intrusion might be responsible. Any air sampling planned at your home or business requires your permission.

What happens if a vapor intrusion problem is found?

If soil or groundwater contaminated with volatile chemicals poses a health concern, the most common solution is to install a system that removes the chemicals before vapors enter a home or business. These systems are similar to those installed in homes where radon is an issue and are commonly known as soil vapor vacuum systems.

Soil vapor vacuum systems remove the volatile chemicals from the soil below the foundation by drawing the vapors out of the soil. The vapor is moved through pipes and discharged into outdoor air. If the chemical levels are high, the vapors are treated before being discharged. When such systems are needed, the party responsible for contamination typically bears the costs.

Content Source: Washington State Department of Health

© Cascade Radon, Inc. 2017