Abstract: A method and apparatus for balancing the inlet air flow against the exhaust air flow in a system for exhausting contaminant-laden air from a work space. The volume of inlet air is controlled in accordance with its temperature so that the weight rate of air through the inlet fan is set at a value approximating the actual or a selected average value of the weight rate of air per minute exhausted by the exhaust fan.

Abstract: A recirculating exhaust hood for a dishwasher may be comprised of an exhaust duct, a positive pressure plenum, a negative pressure plenum, and a fan for circulating air from the communicating dishwashing cavity through the positive and negative pressure plenums, and the exhaust duct. Air drawn through the intake of the fan is circulated through the positive pressure plenum to a supply slot. High velocity air exiting from the supply slot to a contiguous intake port of the negative pressure plenum creates a high velocity stream of air which by entrainment or by Venturi effect draws warm moisture laden air from the dishwashing cavity into the negative pressure plenum. The entrained moist warm air is then recirculated to the positive pressure plenum by means of the fan. A portion of the output of the fan is directed to an exhaust duct and removed from the dishwashing system.