NozzlerownBias is a toolkit for tunnel air and smoke control. It helps you set jet fan spacing so airflow stays even and avoids swirl. See how smoke moves under the ceiling and how much clear height you need. Pick the right Saccardo nozzle size and angle to push smoke the right way at portals. Check how heat and height create stack effect that can bias the flow. Map pressure drops along the tunnel, including roughness, slope, and obstacles. Plan for fires with easy HRR ranges, critical smoke speed, and backlayer length. Estimate safe escape time for people and the smoke temperature at the crown.