WAC 296-307-50015. Local exhaust hoods and booths

Mechanical local exhaust ventilation may be provided by either of the following: (1) Freely movable hoods intended to be placed by the welder as near as practical to the work being welded and provided with a rate of airflow sufficient to maintain a velocity in the direction of the hood of 100 linear feet per minute in the zone of welding when the hood is at its most remote distance from the point of welding. The rates of ventilation required to accomplish this control velocity using a 3-inch wide flanged suction opening are shown in the following table: Welding zone Minimum air flow cubic feet/minutes Duct diameter inches 4 to 6 inches from arc or torch 150 3 6 to 8 inches from arc or torch 275 3-1/2 8 to 10 inches from arc or torch 425 4-1/2 10 to 12 inches from arc or torch 600 5-1/2 Welding zone Minimum air flow cubic feet/minutes Duct diameter inches 4 to 6 inches from arc or torch 150 3 6 to 8 inches from arc or torch 275 3-1/2 8 to 10 inches from arc or torch 425 4-1/2 10 to 12 inches from arc or torch 600 5-1/2 1 When brazing with cadmium bearing materials or when cutting on such materials increased rates of ventilation may be required. 2 Nearest half-inch duct diameter based on 4,000 feet per minute velocity in pipe. 1 When brazing with cadmium bearing materials or when cutting on such materials increased rates of ventilation may be required. 2 Nearest half-inch duct diameter based on 4,000 feet per minute velocity in pipe. (2) A fixed enclosure with a top and at least two sides that surround the welding or cutting operations and with a rate of airflow sufficient to maintain a velocity away from the welder of not less than 100 linear feet per minute.