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In brazing, there is always the possibility of dangerous fumes and gases rising from base metal coatings, ink and cadmium-bearing filler metals, and from fluorides in fluxes. The following well-tested precautions should be followed to guard against any hazard from these fumes.
- Ventilate confined areas. Use ventilating fans and exhaust hoods to carry all fumes and gases away from work, and air supplied respirators as required.
- Clean base metals thoroughly, A surface contaminant
of unknown composition on base metals may add to fume
hazard and may cause a too rapid breakdown of flux, leading
to over heating and fuming.
- Use sufficient flux. Flux protects base metals and filler
metal during heating cycle. Full flux coverage reduces
fuming. Also, consult your MSDS regarding specific hazards
associated with brazing flux.
- Heat metals broadly. Heat the base metals broadly and
uniformly. Intense localized heating uses up flux, increases
danger of fuming. Apply heat only to base metals, not
to filler metal (direct flame on filler metal causes overheating
and fuming).
- Know your base metals. A cadmium coating on a base metal
will volatilize and produce toxic fume during heating.
Zinc coatings (galvanized) will also fume when heated.
Learn to recognize these coatings. It is recommended that
they be removed before parts are heated for brazing.
- Know your filler metals. Be especially careful not to
overheat assembly when using filler metals that contain
cadmium. Consult the Material Safety Data Sheet for maximum
recommended brazing temperatures of a specific filler
metal. The filler metal carries a warning label. Be sure
to look for it and follow the instructions carefully.
(For other safety considerations,
see the American National Standard Z49.1, "Safety in Welding
and Cutting", published by the American Welding Society (AWS),
550 N.W. LeJeune Rd., Miami, Florida 33126.)
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