ANSI/AARST SGM-SF-2017 rev.12-20 specifies practices, minimum requirements and general guidance for reducing soil gas entry into existing homes in order to mitigate occupant exposures to certain hazardous soil gases, including radon gas, chemical vapors and other hazardous gases. This standard of practice addresses a wide range of mitigation methods and additionally provides guidance for health and safety, system design, system installation, and ongoing stewardship. This standard of practice is applicable to residential structures to include: those not more than three stories above grade in height; those often classified as single-family structures; and those that contain not more than four attached dwelling units on a contiguous foundation.