ASD Systems SGM-SF 2017 13 Soil Gas Mitigation Standards for Existing Homes 7.4.8 Straight-line trajectory: Not directed in a straight- line trajectory toward any location that people are likely to congregate in or any passive or active component of a ventilation system such as a window, door or mechanical air intake opening that is less than 20 feet (6 m) away from the point of discharge; 7.4 . 9 Discharged air: Configured to discharge air upward without obstruction. The exhaust discharge shall not be installed in a manner that exhausts downward; and 7.4.10 Damage to building materials: Not installed in a manner that allows exhaust airflow to directly strike building materials such as exterior walls or roof eaves. High moisture content of discharged air can result in ice formation and water damage to building materials. 7.4.11 Horizontal trajectory Informative Advisory—Horizontal trajectory should be avoided. For the purposes of this document, 90-degree horizontal discharge configurations are classified as discharging horizontally even though some portion of exhaust air is reflected downward. The Contractor should consider the fact that horizontal dispersion and slowed velocity of discharged air reduces the distance that radon, soil air and vapors are carried away from occupants and the building. 90-Degree Horizontal Discharges The point of discharge shall be not less than 20 feet (6 m) above grade nearest the point of discharge and not less than a 10-foot (3 m) radius distance away from openings in the building. (See Section s 7.4.3 and 7.4.4 ). Diffused Horizontal Discharges (e.g., rain caps) The point of discharge shall be not less than 15 feet (4.6 m) above grade nearest the point of discharge and 4 feet (120 cm) above, or not less than 15 feet (4.6 m) away from operable windows, doors or other passive ventilation openings into the occupiable portion of the structure or an adjacent structure. 7.4.12 Protection from the elements Informative—Include efforts to: a) Provide support directly below fan locations and the discharge location that is adequate to ensure structural integrity of the pipe configuration. For example, a support hanger, strapping or other physical support means should be provided within 3 feet (91 cm) of the point of discharge or within 18 inches (46 cm) above and below fans located in attics when pipe configurations might otherwise allow lateral or vertical movement of duct piping. Figure 7.4.8 Figure 7.4.9 Figure 7.4.10 Figure Figure Figure 7.4.12 Figure 7.4.11