In confined spaces or indoors, you must perform welding or cutting operations involving metals coated with mercury-bearing materials, including paint, using local exhaust ventilation or airline respirators unless atmospheric tests under the most adverse conditions show that employee exposure is within the acceptable concentrations specified by chapter 296-841 WAC. You must perform such operations, when done outdoors, using respirators certified for this purpose by NIOSH under 24 C.F.R. Part 84.