Radon Mitigation in Large BuildingsThe presence of dangerous radon gas levels in large buildings such as hospitals, airports, office buildings, warehouses, schools, factories, etc. is an issue that has been largely ignored in the recent past. Radon gas exposure over time is known to cause lung cancer, and with most Americans spending anywhere from 40-60 hours a week in these types of buildings, the probability of long term exposure to a hazardous radon level is very high. If the building you own, or work in tests above the EPA radon action level of 4.0pCi/L, a radon mitigation system will need to be installed to remediate the issue. Radon mitigation is the process of drawing out the rising radon gas in the soil underneath the structure by creating a negative pressure with a specially designed in-line radon fan. Certain techniques and processes need to be applied when working with larger commercial buildings in comparison to a simple residential home installation. Lifetime Environmental Solutions has been in the radon mitigation business for over two decades and is certified for commercial radon mitigation by the National Radon Proficiency Program (NRPP) as well as the American Association of Radon Scientists and Technologists (AARST). Trust your properties’ radon mitigation needs with the most knowledgeable and friendly radon experts in the country! Give us a call for a free consultation!
Active Soil Depressurization in Large BuildingsActive soil depressurization (ASD) systems depressurize the soil underneath a structure by drawing in the air and soil gasses from below the slab or a sealed vapor barrier, and vents it above the roofline through a 3-6 inch PVC pipe and an in-line radon fan. The preferred methods of achieving depressurization underneath a structure are sub-slab depressurization, sub-membrane depressurization, and block wall depressurization.
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Sub-slab Depressurization System Installed on a Large Apartment Building
Sub-slab Depressurization:
The EPA defines a sub-slab depressurization system as "a system designed to achieve lower sub-slab air pressure relative to indoor air pressure by use of a fan-powered vent drawing air from beneath the slab." This should cause the radon gas and other toxic gases rising from the soil to flow towards and into the piping to vent out above the roofline. A properly installed sub-slab depressurization system will prevent most of the radon gas coming up from the soil beneath the building from entering the structure above. There are multiple ways to achieve sub-slab depressurization depending on how the structure is built.
For slab on grade properties, multiple collection points must be dug under the slab to pull the air from the entire foundation (the amount of collection points needed depends on the size of the structure and sub slab material). However, if the structure has a drain-tile system under the slab, the piping and fan can pull air freely through that system once, if present, the sump crock is sealed down and the piping is attached directly to the drain-tile. Buildings with drain-tile can achieve a higher level of depressurization much easier because of the field extension the drain-tile generally provides.
Sub-membrane Depressurization
For larger buildings that do not have a slab or only a partial slab on the lowest level (usually in a crawlspace), a vapor barrier (membrane) must be laid and sealed air tight over the soil to prevent gases from entering. Once the vapor barrier is in place, collection points are created underneath the barrier similar to a traditional sub-slab depressurization (SSD) system and the soil gasses are drawn out from under the barrier through those collection points to prevent any further radon entry.
Block Wall Depressurization
In some properties radon can enter through the inside hollows of a block wall. The block wall acts as a passive soil vent that causes radon to actively enter the property at an accelerated rate. For block wall depressurization, the tops of the blocks must be sealed down, and a collection point is added to the block to ensure that the soil gas accesses are depressurized and vented to an appropriate location above the roof line on the exterior of the building. This method is commonly used in tandem with sub-slab depressurization.
The EPA defines a sub-slab depressurization system as "a system designed to achieve lower sub-slab air pressure relative to indoor air pressure by use of a fan-powered vent drawing air from beneath the slab." This should cause the radon gas and other toxic gases rising from the soil to flow towards and into the piping to vent out above the roofline. A properly installed sub-slab depressurization system will prevent most of the radon gas coming up from the soil beneath the building from entering the structure above. There are multiple ways to achieve sub-slab depressurization depending on how the structure is built.
For slab on grade properties, multiple collection points must be dug under the slab to pull the air from the entire foundation (the amount of collection points needed depends on the size of the structure and sub slab material). However, if the structure has a drain-tile system under the slab, the piping and fan can pull air freely through that system once, if present, the sump crock is sealed down and the piping is attached directly to the drain-tile. Buildings with drain-tile can achieve a higher level of depressurization much easier because of the field extension the drain-tile generally provides.
Sub-membrane Depressurization
For larger buildings that do not have a slab or only a partial slab on the lowest level (usually in a crawlspace), a vapor barrier (membrane) must be laid and sealed air tight over the soil to prevent gases from entering. Once the vapor barrier is in place, collection points are created underneath the barrier similar to a traditional sub-slab depressurization (SSD) system and the soil gasses are drawn out from under the barrier through those collection points to prevent any further radon entry.
Block Wall Depressurization
In some properties radon can enter through the inside hollows of a block wall. The block wall acts as a passive soil vent that causes radon to actively enter the property at an accelerated rate. For block wall depressurization, the tops of the blocks must be sealed down, and a collection point is added to the block to ensure that the soil gas accesses are depressurized and vented to an appropriate location above the roof line on the exterior of the building. This method is commonly used in tandem with sub-slab depressurization.
Radon Mitigation Installation
Larger buildings require extra steps and materials to achieve the depressurization needed to adequately decrease the radon levels throughout. Once a building has been properly tested for radon and it has been determined that mitigation is necessary, you must first contact a certified radon professional (Lifetime Environmental Solutions) to conduct a nondestructive investigation of the property to determine a plan of action. Providing construction drawings and information of possible hazards within the structure is vital to the creation of a solid proposal. Once the radon professional has gathered all of the information he/she can that is pertinent to the creation of a proper radon mitigation system, they will need to conduct some diagnostic testing of the property. The main diagnostic method used by radon professionals is sub-slab pressure field extension (PFE) testing. PFE testing basically measures the pressure extension underneath the slab in multiple locations throughout the structure. This is done by creating one/multiple pressure points beneath the slab, then you would drill very small holes into the slab and measurement the pressure at each location. The reason this is done is to ensure sufficient vacuum pressure and collection points are implemented for proper mitigation, essentially securing proper system design. Once the PFE testing is completed, the mitigator can determine what type of ASD system will be the most effective. Those ASD methods are described in detail in the previous section. The next step after implementing an ASD method is to apply the proper piping and mitigation fan for ventilation. Most buildings will be mitigated with PVC piping but some buildings may require a different material such as ABS or stainless steel piping depending on other hazardous chemicals that may be present in the soil, or interior, that could deteriorate or damage PVC over time. The size/type of mitigation fan and amount of fans required is determined by the results of the PFE tests and subsequent follow up tests once the installation is complete. The ventilation points must follow certain codes to guarantee that there is no re-entry of radon gas. The vent must extend at least 6 inches above the gutter line, or in the case of a flat roof it must extend 18 inches above the roof. Systems can be routed to the exterior and run entirely up the exterior wall, or run through an interior wall with the fan placed in a non-livable attic with the vent penetrating through the roof. The ventilation run is chosen during the initial investigation of the property, with the input of the building owner, and in accordance with AARST and NRPP regulations. Give Lifetime Environmental a call today to get started with the mitigation process!
