How much of a respiratory hazard can a piece of metal be? After all, you can’t inhale a piece of metal…or can you?
Isn’t it ridiculous to require a Material Safety Data Sheet on something as inert as metal? Not really.
While metal may be rather harmless at room temperature, when heated it can release fumes.
Fumes, which are defined as vaporized metal (like water turning to steam) can be inhaled and carry toxic contaminants.
Welding fumes contain oxides of the metals in the material being welded.
Fluxes containing silica or fluoride produce amorphous silica, metallic silicates and fluoride fumes.
Fumes from mild steel welding contain mostly iron with small amounts of additive metals (chromium, nickel, manganese, molybdenum, vanadium, titanium, cobalt, copper etc.).
Stainless steels have larger amounts of chromium or nickel in the fume and lesser amounts of iron.
Nickel alloys have much more nickel in the fume and very little iron.
To protect your health and the health of those around you, these fumes should be captured or minimized before they are released into the breathing zone, and the proper respiratory protection should be worn. In order to minimize the fumes generated during brazing, you must know and apply the following do’s and don’ts:
*** DON’TS ***
1. Don’t braze on a dirty part. The unknown dirt on the part may also be toxic. Dirt can cause rapid overheating and a breakdown of the flux, releasing fumes. Remove coatings from the weld area to minimize the fume. The removal of coating will also improve weld quality.
Use stripping products to remove coatings. Make sure to remove any residues before welding.
Use wet slurry vacuum removal techniques for removing very toxic coatings.
Do not grind coatings. Grinding dust may be toxic.
2. Don’t braze without good flux coverage. The lack of flux exposes more oxidized metal which increases fuming.
3. Don’t overheat the base metal or filler rod. Overheating can increase fume release.
4. Don’t braze on unknown or cadmium plated material. Cadmium and zinc (galvanized) coatings are often found in certain applications. These toxic metals fume readily when heated.
Be sure to remove these coatings before applying the heat.
Coatings should be removed mechanically. Don’t attempt to burn them off.
5. NEVER braze in an enclosed or confined space without making provisions for adequate ventilation. Failure to do this could be FATAL.
6. Respiratory protection is needed when ventilation is not sufficient to remove welding fumes or when there is risk of oxygen deficiency. Select and use respirators or supplied air in compliance with your workplace regulation. Seek expert advice and initiate a proper respiratory protection program.
*** DO’S ***
1. All Respirators MUST be CSA Standard Z.94.4, Selection, Use and Care of Respirators. 2. Make sure the parts are clean before you start. Don’t try to let the flux do the cleaning job. 3. Completely cover the joint area and filler rod with flux. This helps protect both from oxidation which minimizes fume release. 4. Apply heat uniformly and don’t overheat. Heat the base metal, not the filler rod. Proper temperature is important. Under-heating will produce balling and no flow. 5. Overheating will produce excess fumes. So what can happen if you inhale fumes? Of course it varies as to the type of fume, exposure time, and amount. Most commonly you will suffer from “metal fume fever” or “toxic fume syndrome”. This is usually characterized by fever and chills occurring between 4-12 hours after exposure. These symptoms will typically clear up in one or two days. In addition to these outward symptoms, there may be other effects brought on by the toxins.
Protect yourself. Only braze in areas with good ventilation and wear a respirator approved for protection against fumes.