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Structural Repair

Cutting and Welding

Welding is used to join metal surfaces. Most autobody shops have an arc welder for this purpose (heliarc or MIG welding). An arc welder produces an electrical arc between a welding rod and the metal parts to be joined. This arc is so hot that it melts and even vaporizes some of the metal in its path. The melted metal hardens to form the weld and join the parts. Cutting is performed with an intense electrical arc which burns right through metal.

Welding "smoke" can contain toxic metals such as lead or chromium.

Hazards of cutting and welding

Vaporized metal produced while cutting or welding immediately condenses in the air, forming very small particles which we see as smoke. These particles are easily inhaled. Anything that coats the metal where the weld or cut is made, such as old paint residues, will end up in the air. Old paint residues may contain lead, chromium and other toxic materials and if particles containing these hazardous materials are inhaled, your body’s lungs, nervous system and other organs, such as the liver or kidneys, may be harmed. Even at very low exposure levels, lead has been shown to cause depression and sleep disorders. Chromium has been linked to lung cancer. Exposure to these metals has been shown to exceed safe levels in auto repair shops when coatings are directly welded or cut.

In addition to these particulates, arc welding and cutting also produces the gases ozone and nitrogen oxides which are very irritating to the respiratory system.

Grind off old paint and weld only on bare metal.

Decreasing exposures

To decrease your exposures while cutting and welding, you should:

  • grind off any coating, creating a bare metal surface two to four inches around the surface to be welded or cut
  • for infrequent short-term welding or cutting jobs on clean steel surfaces, use general ventilation, such as a wall fan [ the fan should move 2000 cubic feet of air per minute per welder]
  • for more frequent or longer-term operations, or operations involving coated metals, toxic welding rods or fluxes, a local exhaust ventilation system consisting of a hood and flexible duct may be required (read more…).
HEPA filters protect you from welding fume.

The welding mask does not protect you from breathing harmful particles in the air! To protect yourself while welding or cutting, special welding respirators are sold to fit under the welder’s shield. A half mask respirator fitted with HEPA cartridges or an N-100 filtering face piece (dust mask) may also be worn. Since welding is usually done on the shop floor, nearby workers may also need to be protected.

A welding shield protects your eyes from welder's flash.

Welder’s flash

UV light from the welding arc can burn a part of your eye called the retina. The pain from “welder’s flash,” often described as having sand in your eye, usually occurs at home hours after welding was done. Welders must wear goggles or face shields with an appropriate dark filter plate over the eyes to protect them. What’s more, even bystanders can accidentally look at the bright arc and hurt their eyes, so a plastic curtain with a UV absorbing substance (called a welding curtain) should be used around the welding area to protect them.

Leather gloves, fire retardant long sleeved coveralls, and high top leather shoes are also worn to protect the skin from heat and sparks.

Grinding produces dust which may contain lead and chromium.


Hazards of grinding

Grinding old paint and rust creates lots of irritating dust that is easily inhaled and can get in your eyes. It can also get into your mouth. We don’t think anyone eats the dust on purpose, but it can easily stick to your hands and face, and if not washed off, will contaminate food, drinks and cigarettes which are put in your mouth.

The dust produced during these operations may contain lead and chromium, as well as grit from the sanding disks. These hazardous materials can be harmful to your lungs and nervous system. At even very low levels, lead has been shown to cause depression and sleep disorders. Chromium has been linked to lung cancer. Auto repair workers performing these tasks without appropriate precautions have exceeded safety levels of exposure to these hazardous materials.

How much lead is harmful? OSHA has set a limit on how much lead a person should breathe in during 8 hours of work to prevent harm [50ug/m3 of air]. That adds up in a day to an amount of lead the size of one grain of sand!

Coveralls, gloves, goggles and respirator keep particles out of your eyes and mouth and off your skin.

Decreasing exposures

To protect yourself while grinding:

  • wear coveralls, goggles, gloves and a respirator with a HEPA filter - the pink/purple colored one
  • use wet methods and locally-exhausted grinding tools to really cut down the amount of dust produced
  • don’t track dust all over the shop where others might be exposed
  • always wash your hands, arms and face thoroughly with soap and water when finished, when using the restroom, and definitely before leaving for coffee breaks and lunch