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 |
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.
[Statutory Authority: RCW
49.17.010,
49.17.040,
49.17.050, and
49.17.060. WSR 20-21-091, § 296-307-50015, filed 10/20/20, effective 11/20/20. WSR 97-09-013, recodified as § 296-307-50015, filed 4/7/97, effective 4/7/97. Statutory Authority: RCW
49.17.040, [49.17.]050 and [49.17.]060. WSR 96-22-048, § 296-306A-50015, filed 10/31/96, effective 12/1/96.]