The objective of this program was to develop design criteria for local exhaust systems which would assure the effective capture and removal of toxic contaminants emanating from open surface tanks. In a literature survey of the topic it was found that practically all of the exhaust hoods used by industry for open surface tanks were of the lateral or semilateral type. By exhausting from only one side of a tank, ample space is available above the tank for baskets, conveyer mechanisms and other devices. In developing the new criteria the experimental studies took into account the trends towards: high gassing rates due to increased plating current densities, the use of surface control agents such as plastic balls, push pull ventilation methods for wide tanks, and air agitated tanks. Variables included in the evaluation were hood design, tank width to length ratio, liquid and temperature level, exhaust flow rate, slot velocity, evaporation, air agitation, passing rates, cross drafts, and makeup air introduction method.