SGM-SF_2017with 12/20 Revisions

ASD (revised 12/20) 17 ANSI/AARST SGM-SF 2017 (with 1220 revisions) Soil Gas Mitigation Standards for Existing Homes 6.3 ASD Pipe Sizing ASD duct piping shall be sized and configured to result in adequate capacity to transport the volume of air required for establishing a vacuum under each slab or membrane and within each airspace being depressurized by the ASD system. 6.3.1 Minimum inside diameter—air volume capacity ASD duct piping from the exhaust point to the soil gas collection plenum(s) shall be equivalent or greater than the cross-sectional area of a 3-inch (75-mm) ID pipe or as determined by PFE Analysis. 6.3.2 When larger air volume needs are indicated Where PFE Analysis indicates the necessary airflow for the entire system is more than 80 cubic feet per minute (cfm) (2.3 m 3 /min), duct piping from the exhaust point to the soil gas collection plenum(s) shall be equivalent or greater than the cross-sectional area of a 4-inch (100-mm) ID pipe. 6.3.3 When smaller air volume needs are verified Where PFE Analysis indicates the necessary airflow for the entire system is equal to or less than 40 cfm (1.1 m 3 /min), 2-inch (50-mm) ID duct piping from the exhaust point to the soil gas collection plenum(s) is permitted. If airflow exceeds 40 cfm (1.1 m 3 /min) due to fan pressures much stronger than normally employed, such as greater than 6 inches WC (1500 Pa), 2-inch (50-mm) ID pipe is only permitted if both: a) The system still meets the needs for an appropriate design, as described in Section 5.3 ; and b) Adequate air volume transport is achieved for establishing a vacuum within each airspace being depressurized. 6.3.4 Equivalent cross-sectional area Multiple pipes of various sizes that are joined in a parallel manner to result in a combined air volume capacity that is not less than the equivalent cross-sectional area of pipe diameters required in Sections 6.3.1 and 6.3.2 shall be permitted. The minimum pipe diameter through parallel pipe sections shall be 2-inch (50-mm) ID pipe. Note—Three 2-inch (50-mm) pipes in parallel are necessary to meet this requirement when connecting to a single 3-inch pipe. 6.3.5 Maintain whole-system air volume capacity The configuration shall not reduce duct pipe diameters or dimensions in the direction of airflow from the soil gas inlet(s) to the exhaust location to result in less whole-system air volume capacity than achieved with pipe sizes specified in Sections 6.3.1 , 6.3.2 or 6.3.3 . All components of the ducting system that reduce air volume transport capacity shall be accounted for in meeting this requirement, to include any rain caps or other obstructions at exhausts and circumference or size of slab penetration connections to soil gas. 6.3.6 Multiple suction points Each suction pipe shall be sized to provide air volume capacity sufficient to establish a vacuum under each slab or membrane and within each airspace being depressurized by the ASD system. Where air valves, dampers or baffles are used to adjust airflow balance: a) their location, settings and design shall be included in “as built records” for the system; and b) they shall be marked or labeled to indicate their purpose, settings and instructions, such as “Radon System Air Valve. Do Not Alter From Marked Setting,” or similar wording. 6.3.6.1 Drainage When multiple suction points are employed, piping extended to secondary suction pits exclusively designed for condensate or rainwater drainage do not require any specific pipe diameter. Informative Table 6.3.4 Cross-sectional Area Dimensions ID (inner diameter) Cross-sectional Area 2-inch (50-mm) 3.1 sq. in. (20 cm 2 ) 3-inch (75-mm) 7.1 sq. in. (46 cm 2 ) 4-inch (100-mm) 12.6 sq. in. (81 cm 2 ) 6-inch (150-mm) 28.3 sq. in. (182 cm 2 )