Type II hoods shall be constructed of steel not less than 0.030 inch (0.76 mm) (No. 22 Gauge) in thickness, stainless steel not less than 0.024 inch (0.61 mm) (No. 24 Gauge) in thickness, copper sheets weighing not less than 24 ounces per square foot (7.3 kg/m
2
), or of other approved material and gauge.