Diagnostics
It is extremely important to perform diagnostics to determine what type of material is under the floor and how the HVAC system(s) may influence how soil gas is distributed throughout the building. Whenever available, we will study architectural building plans for as much information as possible as it pertains to the mitigation approach.
Pressure field extension (PFE) testing is a common diagnostic tool. Performing the PFE test will help us diagnose the type of material below the slab, how air moves under the slab, and how far the coverage will be. Using a manometer, we will determine the amount of air required to develop a minimum negative pressure of .0004 in of water column at each test port. We can then design the system with the correct amount of suction points, correct pipe size and correct fan size. Vapor entry routes should be sealed prior to PFE testing. Designs can be performed on smaller buildings at time of installation if all building conditions are known and acceptable, but it is infrequent.
If we are installing the system during the construction phase of a new building, we will consult the client on the proper materials needed for a successful system and design the system accordingly. Again, these steps are critical in order to save the client the added expense of an under or over-designed system.
We will also collaborate with building engineers and/or HVAC specialists to determine how the HVAC system is operated and which occupants have access to its operation. We will inquire about how the system is balanced and if fresh air intakes are being used. It is not uncommon for us to find that one of the main occurrences of soil gas entry is due to the HVAC system putting the building under extreme negative pressure. This problem can severely diminish the effectiveness of a vapor intrusion system.
Note: Building zonal pressure testing is often recommended to determine how pressure inside compared to the outside changes during different demands on the HVAC system. If the building operates in negative pressure equal to or greater than 0.01 inch of water column, then the vapor intrusion system would be compromised during those periods.
Installation
Once we have performed field diagnostics and finalized the design, the mobilization process can begin. In existing buildings, it is important to locate any buried gas lines, electrical conduit, ductwork, rebar, footings, pipes, or other potential conflicts. The slab depth will also be noted. We perform this step with ground penetrating radar (GPR). In buildings with radiant heat lines buried below the slab, we will locate the lines with a thermal imaging camera. Reducing risk to the building and its occupants inherently reduces cost.
In existing buildings, openings will be created in the slab via professional concrete coring to accommodate any pipe diameter. At least 2 cubic feet of material extending at least 6 inches below the slab will be excavated from each core site. In new construction, a drain tile network is designed and installed into trenches dedicated to the vapor intrusion system. Suction points can be stubbed-in to the drain tile prior to the concrete pour for us to connect to on a later date.
Pipe will be installed utilizing commercial grade hangers and hardware and routed to the exterior and above the roof line or through the building envelope and through the roof. Aerial lifts with trained operators will be deployed as needed. An in-line axial fan will be installed with rubber couplings to assure quiet, reliable operation.
If indicated or requested, our crews will set up a containment area to isolate the workspace from the rest of the building. We can operate a HEPA air scrubber to evacuate the odor of glues and solvents to the exterior as well as any intolerable soil vapor.
Important – System Performance Confirmation
Once the installation is completed, we will perform a system performance confirmation. The system will be considered functioning properly when it can achieve at least .25 inches water column at the suction point and measureable vacuum at the farthest edges of the area under worst case conditions (all exhaust fans and heating systems running during cold weather) as determined by a differential pressure reading of at least -0.003 inches water column below the slab or visible downward flow of air at test holes using chemical or smoke sticks.
It is extremely important to perform diagnostics to determine what type of material is under the floor and how the HVAC system(s) may influence how soil gas is distributed throughout the building. Whenever available, we will study architectural building plans for as much information as possible as it pertains to the mitigation approach.
Pressure field extension (PFE) testing is a common diagnostic tool. Performing the PFE test will help us diagnose the type of material below the slab, how air moves under the slab, and how far the coverage will be. Using a manometer, we will determine the amount of air required to develop a minimum negative pressure of .0004 in of water column at each test port. We can then design the system with the correct amount of suction points, correct pipe size and correct fan size. Vapor entry routes should be sealed prior to PFE testing. Designs can be performed on smaller buildings at time of installation if all building conditions are known and acceptable, but it is infrequent.
If we are installing the system during the construction phase of a new building, we will consult the client on the proper materials needed for a successful system and design the system accordingly. Again, these steps are critical in order to save the client the added expense of an under or over-designed system.
We will also collaborate with building engineers and/or HVAC specialists to determine how the HVAC system is operated and which occupants have access to its operation. We will inquire about how the system is balanced and if fresh air intakes are being used. It is not uncommon for us to find that one of the main occurrences of soil gas entry is due to the HVAC system putting the building under extreme negative pressure. This problem can severely diminish the effectiveness of a vapor intrusion system.
Note: Building zonal pressure testing is often recommended to determine how pressure inside compared to the outside changes during different demands on the HVAC system. If the building operates in negative pressure equal to or greater than 0.01 inch of water column, then the vapor intrusion system would be compromised during those periods.
Installation
Once we have performed field diagnostics and finalized the design, the mobilization process can begin. In existing buildings, it is important to locate any buried gas lines, electrical conduit, ductwork, rebar, footings, pipes, or other potential conflicts. The slab depth will also be noted. We perform this step with ground penetrating radar (GPR). In buildings with radiant heat lines buried below the slab, we will locate the lines with a thermal imaging camera. Reducing risk to the building and its occupants inherently reduces cost.
In existing buildings, openings will be created in the slab via professional concrete coring to accommodate any pipe diameter. At least 2 cubic feet of material extending at least 6 inches below the slab will be excavated from each core site. In new construction, a drain tile network is designed and installed into trenches dedicated to the vapor intrusion system. Suction points can be stubbed-in to the drain tile prior to the concrete pour for us to connect to on a later date.
Pipe will be installed utilizing commercial grade hangers and hardware and routed to the exterior and above the roof line or through the building envelope and through the roof. Aerial lifts with trained operators will be deployed as needed. An in-line axial fan will be installed with rubber couplings to assure quiet, reliable operation.
If indicated or requested, our crews will set up a containment area to isolate the workspace from the rest of the building. We can operate a HEPA air scrubber to evacuate the odor of glues and solvents to the exterior as well as any intolerable soil vapor.
Important – System Performance Confirmation
Once the installation is completed, we will perform a system performance confirmation. The system will be considered functioning properly when it can achieve at least .25 inches water column at the suction point and measureable vacuum at the farthest edges of the area under worst case conditions (all exhaust fans and heating systems running during cold weather) as determined by a differential pressure reading of at least -0.003 inches water column below the slab or visible downward flow of air at test holes using chemical or smoke sticks.
