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Ventilation - Figure 5

Illustration of canopy receiving hood not controlling vapors from an unheated tank.Exhaust volume = 1000 CF/M; Hood-tank distance=4 ft.
  1. Canopy designed as receiving hood will not control vapors from unheated tank.
Illustration showing how airflow needs to be increased to use capturing hood over unheated process. Exhaust volume=8500 cf/m; hood-tank distance: 4 ft.  
  1. Airflow must be increased 850% to use canopy as a capturing hood over unheated process.

Contaminant overflow when more contaminated air enteres a hood than what the fan exhausts. Of 800 CF/M rising, 500 CF/M exhausts and 300 CF/M overflows around the outside of the hood.

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

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