745 Welding, Cutting, and Brazing Safety

Ventilation in Confined Spaces

Dangerous metals requiring ventilation while welding, cutting, and brazing in confined spaces include the following:

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 American Conference of Governmental Industrial Hygienists (ACGIH) sets the threshold limit value (TLV) at .02 milligrams per cubic meter (mg/m³) over an 8-hour work period, OSHA's Permissible Exposure Limit (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. This is required 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: The following requirements apply:

• In confined spaces, welding involving lead-base metals (erroneously called lead-burning) must be done in accordance with 1910.252(c)(4).
• In areas immediately hazardous to life and health (IDLH), a full-facepiece, pressure-demand, self-contained breathing apparatus (SCBA) or a combination full-facepiece, pressure-demand supplied-air respirator with an auxiliary, self-contained air supply approved by NIOSH under 42 CFR part 84 must be used.
• Indoors, welding involving lead-base metals must be done in accordance with OSHA 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.

Zinc: In confined spaces, welding or cutting involving zinc-bearing base or filler metals, or metals coated with zinc-bearing materials must be done in accordance with paragraph OSHA 1910.252(c)(4), .

To see more information on the various chemicals listed above, you can visit the OSHA's Occupational Chemical Database.

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