Figure 5.  A capturing hood requires sufficient airflow to reach outside of the hood to capture contaminants.

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  1. Canopy designed as receiving hood will not control vapors from unheated tank.
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  1. Airflow must be increased 850% to use canopy as a capturing hood over unheated process.

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  1. "Overflow" of contaminants from a receiving hood occurs if more contaminated air enters the hood than the fan exhausts.