What specification must be met for ducts in subslab soil exhaust systems?

For subslab soil exhaust systems, ducts must terminate upward to effectively expel gases and vapors that can accumulate beneath a building. This upward termination helps prevent the accumulation of hazardous substances within the system and ensures that pollutants are vented away from the living spaces of the building. Additionally, terminating ducts upward minimizes the potential for backdrafts and re-entry of contaminated air, thereby promoting a safer indoor environment.

While factors such as insulation, fire-resistance, and accessibility are important in different contexts or applications, the primary requirement for subslab soil exhaust systems is that the ducts effectively direct airflow away from the structure. Therefore, the upward termination of ducts is pivotal for proper ventilation and maintaining air quality in the building.