30% mixed — 70% recirculation. UV runs effectively multi-pass; treated air is mixed with fresh in the supply duct.
Air 0.37 m/s Contact 5400 ms Walk-in AHU Reflection ×1.50
Wall material: Stainless steel 2B (matt)
(25% reflective). Reflection boost: ×1.50 = 1 + 2 × 0.25 (capped at ×2.5).
Open ends: inlet (Z−) + outlet (Z+) — no contribution.
Engineering approximation for multi-bounce average dose inside the
irradiation length. Higher reflectivity (PTFE 98%, polished
aluminium 72%) = higher boost but capped to avoid resonator-overshoot.