4681 (RP-1168) – Exhaust Contamination of Hidden vs. Visible Air Intakes PDF

A wind tunnel dispersion modeling study was conducted to investigate exhaust contamination of hidden versus visible air intakes. A “hidden” intake is typically on a building sidewall or on the sidewall of a roof obstruction opposite the exhaust source. A “visible” intake is at roof level or on top of an obstruction, directly above the hidden intake. Overall, the study has shown what designers suspected: placing air intakes on building sidewalls is beneficial when the stacks are on the roof. Significant concentration reductions were found when air intakes are placed right below the building roof edge on the building sidewall. The farther down the building sidewall the air intake is placed, the larger the reduction. However, the largest relative reduction between a visible and hidden intake is achieved by just moving the intake a few feet from the edge of the building roof to a point just around the corner on the building sidewall.

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