Modeling Solution for Exhaust Re-Entrainment into Air Intakes Join us for a webinar on the use of an alternative dispersion model (GRAL) to evaluate exhaust re-entrainment into air intakes. The GRAL (Graz Lagrangian) modeling system—an advanced air dispersion model developed by Graz University in Austria. GRAL is designed for complex built environments, such as semiconductor fabs, where standard models like AERMOD fall short in resolving near-field dispersion and building-induced airflow. GRAL simulates wind flow and pollutant transport with CFD-like detail but significantly lower cost and turnaround time. By tracking individual pollutant particles and capturing building wakes and recirculation zones, it offers a practical and accurate solution for evaluating the risk of exhaust re-entrainment into air intakes which is critical for facilities, environmental compliance, and quality control. The session will demonstrate how GRAL supports stack design, process layout, and emissions management. Hector Machado is a Chemical Engineer with over seven years of experience in air quality assessment and air dispersion modeling. He has extensive experience in air dispersion and meteorological modeling using CALPUFF, GRAL, AERMOD, WRF, and TAPM. His work has supported environmental permits and development approvals for industrial, commercial, and infrastructure projects in Australia, as well as air permitting and modeling projects in the United States. He is also experienced in assessing exhaust re-entrainment and building wake effects using GRAL.