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Important Things To Consider Before Vapor Intrusion Testing

Overview of Vapor Intrusion

Vapor Intrusion (VI) occurs when volatile chemicals diffuse upwards from contaminated groundwater or soil into buildings and the environment. There are three different vapor intrusion pathways into buildings above a chemical contamination. Any of these pathways will allow dangerous vapors to find their way into buildings. How concentrated these volatile compound vapors are will vary widely depending on numerous factors. However, vapor intrusion will tend to be greater when it can find a preferential pathway and will be greatest with any direct infiltration of a contaminant. However, no pathway is good for the home or business owner, or for inhabitants or workers when vapor intrusion becomes a problem.

The most common source of these dangers is soil vapor intrusion. These soil vapors may come from dump sites in land dumps or from volatile organic compounds that have entered groundwater sources and are now emitting these gasses up through the overhead soil. Human exposure to these chemicals is likely whenever a property or groundwater source has been contaminated with volatile organic compounds (VOCs).

When the US discovered how dangerous volatile organic compounds that had been dumped at certain sites were to human health and the environment, soil vapor investigations were begun with the goal of limiting the risk of exposure at these sites to humans. Since the 1990’s, much of that effort has focused on limiting human exposure to VOCs as a result of soil vapor intrusion. The EPA conducted extensive research to find ways to limit and regulate the use of VOCs and protect people from any exposure to VOCs.

When Should You Consider a Vapor Intrusion Assessment?

Vapor intrusion assessment has two specific goals. The first is to determine whether there is a complete vapor intrusion pathway. And if a clear pathway is found, the second is to determine if the identified vapor contaminants pose a health risk that is dangerous to building occupants. With these goals in mind there are three clear warning signs that vapor intrusion testing is needed in your building or on your property. 

  1. The most obvious warning sign is the presence of vapor intrusion chemicals on your property or in your building. These could be industrial products, cleaning supplies, ingredients for products you produce, volatile organic compounds in the air, etc.  When VOCs are stored in a facility or on the property there is an increased risk of vapor intrusion from unsealed or cracked containers, spills, underground storage tanks and even from leftover paints used to cover building walls or equipment.  
  2. A second warning sign is the discovery of preferential pathways for VOCs into your building. Perhaps there are sewer lines below the building, mine shafts nearby, fractures in your building’s foundation, tunnels, or large conduits for cables; anywhere that gasses can find an easy pathway to diffuse into your building(s).
  3. A third warning sign is the presence of risk factors that are inherent to your property or buildings. These include, but are not limited to; 
    • a low and fluctuating water table 
    • known sources of VOCs in the vicinity
    • changing pressures inside or below the building

Any of these risk factors can create easy pathways for the diffusion of VOCs into your building(s) which should lead you to consider VI assessment as well as potential vapor intrusion solutions.

Factors to Consider Before Vapor Intrusion Testing

The sampling and measuring of indoor air is very complicated because indoor air concentrations have a lot of variables that need to be considered. Outside temperature and barometric pressure, soil temperature and moisture content, levels of groundwater, the type of building construction, the foundation and its integrity, whether preferential pathways exist and the rates of indoor-outdoor air exchange, can all affect how vapor migrates through the soil and its ability to enter a building.

Because indoor air and soil gas sampling results can vary widely and because data collected for analysis is limited, experts within the industry have determined that it is more efficient and protective to health if vapor samples are collected during what are known as “worst-case conditions.” These conditions make it most likely that samples taken will determine whether vapor intrusion is occurring. This is because collecting samples during “worst-case conditions” provides a more accurate understanding of how high the chemical concentrations can get into the indoor air.

There are two factors as to why vapor intrusion investigation and sampling are done only in the summer and the winter.

Doors and Windows Remain Closed
When doors and windows remain shut to keep heat or cold out, and when tenants run their heating, ventilating and air conditioning (HVAC) systems, these are the best conditions for vapor intrusion to occur and to be measured. Factors that keep the indoor air circulating without influxes of outdoor air promote a higher risk of vapor intrusion by allowing any VOCs entering the building or house to accumulate without being diluted by influxes of fresh outside air. There is also some evidence that running your HVAC system can create a pressure differential by which vapors from the subsurface get pulled up into buildings.

The Water Table Declines
Because chemical contaminations are located below the surface, and water tables tend to drop during the summer and winter months, levels of soil moisture also decrease creating a more porous substrate. When the soil is more porous it allows for more vapors to rise through the soil and collect below or in buildings above the soil. This creates the “worst case conditions” scenario in which there is a higher probability of vapors finding their ways into buildings. This is why summer and winter conditions provide testing laboratories with the most accurate opportunities to collect samples for vapor intrusion assessment.

Where Can You Go to Get Started?

Torrent Laboratory is your partner for all levels and methods of soil vapor assessment. We are always committed to providing our clients with the most innovative testing technologies available anywhere. Our exceedingly experienced engineers will offer the best results for your vapor intrusion assessment project. This commitment includes:

Soil Vapor Testing
Torrent Laboratory offers two types of soil vapor intrusion sampling: regular and low-level reporting.

Our regular TO-15 test method reports at limits as low as 0.5 ppbv, and is sufficient for most soil vapor investigation. However, because of greater human health risks with our residential or commercial environmental screening levels (ESLs), we also offer low-level reporting. We use the TO-15 SIM technique, which is a highly sensitive methodology that can report results to 0.005 ppbv. This makes our low level reporting ideal for the most precise applications.

Ambient Air Testing
With the ongoing evolution of indoor air analysis Torrent offers the very best in ambient air testing. By continually investing in new methods, technologies and procedures, Torrent offers the most advanced testing available. We supply data for a range of air methods, including NIOSH, OSHA, ASTM, and EPA Air Compendium Methods (TO, CO, IO). Our unwavering commitment to the highest quality testing is inspired by our dedication to the continual advancement of testing and analysis, by our growing environmental awareness and accountability and by the needs of our clients.

In addition to our longstanding commitment to quality testing, we are also well known for our customer service and recognized for the fastest turnaround times in the industry.