745 Welding, Cutting, and Brazing Safety

Metals

Manganese: Confined space welding can significantly increase exposure to manganese fumes. The exposure can vary considerably depending on the amount of manganese in the welding wire, rods, flux and base metal. Exposure to manganese may have serious neurological effects. Manganese poisoning or "manganism" is a disease closely related to Parkinson's disease which causes tremors, shaking, and loss of muscle control. Although the ACGIH sets the threshold limit value (TLV) at .02 milligrams per cubic meter (mg/m3) over an 8-hour work period, OSHA's PEL for manganese is 5.0 mg/m3 which is 250 times higher than the TLV. Workers' compensation carriers may require their clients to meet the TLV to reduce risk.

Mercury: In confined spaces or indoors, welding or cutting operations involving metals coated with mercury-bearing materials, including paint, must be done using local exhaust ventilation or airline respirators unless atmospheric tests under the most adverse conditions show that employee exposure is within the PEL for mercury. Such operations, when done outdoors, must be done using NIOSH-approved respirators.

Lead: In confined spaces, welding involving lead-base metals (erroneously called lead-burning) must be done in accordance with 1910.252(c)(4). Indoors, welding involving lead-base metals must be done in accordance with 1910.252(c)(3). In confined spaces or indoors, welding or cutting operations involving metals containing lead, other than as an impurity, or metals coated with lead-bearing materials, including paint, must be done using local exhaust ventilation or airline respirators.

When done outdoors, welding involving lead-based materials must be done using respirators approved for this purpose by NIOSH under 42 CFR part 84.

Zinc: Indoors, welding or cutting involving zinc-bearing base or filler metals coated with zinc-bearing materials must be done in accordance with 1910.252(c)(3).

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