Arc Welding Safety

Every arc welding process puts you next to the same three dangers: light that burns, metal that spatters, and electricity that can stop your heart. Stick, MIG, TIG and flux-cored welders share these hazards, and so does anyone working near them. Fume, fire prevention and gas cylinders have their own rules on top of this.

What You Will Be Able to Do

• Pick a lens shade for the process and amperage.
• Dress so spatter and arc light cannot reach your skin.
• Avoid electric shock from the welding circuit.
• Recognize arc eye and know what to do about it.
• Protect the people working around you.

What the Arc Does to Your Eyes and Skin

A welding arc gives off ultraviolet (UV), visible and infrared light. UV is the most immediate danger because you cannot feel it while it happens.

Arc eye, also called welder's flash or photokeratitis, is a sunburn on the clear front surface of the eye. A short exposure is enough. You may feel fine for several hours, then wake up that night with severe pain, tearing, light sensitivity and a feeling of sand under your eyelids. Symptoms usually start 6 to 12 hours after exposure.

Arc eye usually heals in a day or two, but you should see a doctor or go to urgent care, and report it at work. Repeated exposure and infrared light can cause lasting harm, including damage to the retina and cataracts.

Skin burns the same way. A few minutes of arc light on bare skin can give you a burn like a bad sunburn, and UV light passes through thin or light-colored shirts. Over a career, unprotected UV exposure raises your risk of skin cancer.

Warning: Never look at an arc without a filter lens, even for a second. Reflected arc light off a shiny wall or a bright surface can burn your eyes too.

Choosing a Lens Shade

The shade number tells you how much light the lens blocks. A higher number is darker. OSHA sets the minimum shades in 29 CFR 1910.133. The table below shows those minimums, plus the darker shades that the American Welding Society suggests for comfort at each amperage.

Start with a shade too dark to see the arc zone, then go lighter until you can see the puddle clearly. Never go below the minimum. For a 150 amp MIG weld, the minimum is shade 10, and many welders run shade 11.

Using an Auto-Darkening Helmet

An auto-darkening lens goes dark when its sensors see the arc. Most of these helmets give you UV and infrared protection even when the lens is in its light state, but they rely on batteries and clear sensors.

Before each use:

1. Check that the shade and sensitivity settings fit the job.
2. Check the battery, or the solar charge, per the maker's manual.
3. Test the lens following the maker's instructions.
4. Clean or replace scratched or spatter-covered cover lenses.
5. Keep sensors clear. A glove, a pipe or your own arm can block them when welding out of position.

If the lens flickers or stays light when you strike, stop using it and replace it.

Dressing for the Arc

Clothing is your protection from spatter and UV. The basic rule is simple: no bare skin and nothing that melts.

• Eye protection: Wear safety glasses with side shields under your helmet. When you flip the hood up to chip or grind, you still need eye protection. Flying slag is a common cause of eye injury.
• Jacket or sleeves: Wear flame-resistant cotton or leather, buttoned to the neck and wrists. Leather is best for high amperage and overhead work.
• Gloves: Wear dry, insulated welding gloves in good condition. Heavy gauntlets suit stick and MIG. Thinner leather gives you the feel you need for TIG.
• Pants: Wear heavy cotton or denim with no cuffs, and let them hang over your boots.
• Boots: Wear high-top leather boots with no exposed laces if possible. Low shoes catch spatter.
• Head and neck: A welding cap and a hood with neck coverage stop sparks from reaching your hair and collar.
• Hearing: Wear earplugs or earmuffs around grinding and air carbon arc work. Earplugs also keep hot spatter out of your ear canal during overhead work.

Avoid polyester, nylon and other synthetics. They melt into your skin and burn fast. Also avoid open pockets and cuffs, which catch sparks. Keep lighters out of your pockets, because a hot spark on a butane lighter can make it burst.

Warning: Oily or greasy clothing catches fire easily. Change out of it before you weld.

Electric Shock

Arc welding uses a live circuit that you hold in your hand. Welding machines have an open-circuit voltage, which is the voltage across the output when you are not welding. Common machines run from about 20 volts up to around 100 volts. That can be enough to kill you if your body completes the circuit, and wet skin or sweat lowers your body's resistance.

There are two different shock risks:

• Primary voltage: The 230 to 575 volt power coming into the machine. It is the most dangerous. Only qualified people should open a machine or work on its input wiring.
• Secondary voltage: The welding circuit itself, from the electrode to the work clamp.

Follow these rules on every job:

1. Inspect cables, the electrode holder or gun, and the work clamp. Replace damaged insulation.
2. Make sure the machine is properly grounded, per its manual.
3. Connect the work clamp to clean, bare metal, as close to the weld as you can.
4. Wear dry gloves and dry clothing. Change gloves if they get soaked with sweat.
5. Insulate yourself from the work and from the ground. Stand on a dry rubber mat or dry wood if the floor is damp.
6. Never touch the electrode and the work at the same time with bare skin.
7. Never change a stick electrode with bare hands or wet gloves.
8. Never coil cables around your body or drape them over your shoulders.

Warning: Shock risk goes up sharply in wet locations, on metal structures, and in tight spaces where your body presses against the work. In these conditions, use the machine's voltage-reducing device if it has one, and follow the site's procedure.

Do not weld in the rain or while standing in water. If someone is being shocked, do not touch them. Turn off the power first, then call for help.

Welding current also creates a magnetic field around the cables. People with pacemakers and other implanted devices should talk to their doctor and the device maker before working near welding equipment.

Protecting People Around You

Your arc can burn a coworker's eyes from across the shop. Use welding screens or curtains made for the purpose when others are nearby, and warn people before you strike. Do not assume that a clear plastic curtain blocks enough light, because only rated welding curtains do. If you are helping out, inspecting or tacking, you need eye protection too. Painted walls in a welding area should have a low-reflecting finish, because shiny surfaces bounce UV around.

Other Hazards at the Weld

• Hot metal. A fresh weld and the plate around it can burn through a glove. Use pliers, and mark hot work so others know.
• Chipping and grinding. Slag flies when you chip it. Wear safety glasses and a face shield.
• Compressed gas. Argon and CO2 displace oxygen in tight, low or poorly ventilated spaces, and you will not smell the danger. Shielding gas can leak and collect in pits or tanks.
• Degreasers. Keep chlorinated solvents far from the arc. Arc UV can break down the vapor into phosgene, a highly toxic gas.

Common Mistakes

• Tacking without a helmet. A squint and a flash is enough for arc eye.
• Rolling up your sleeves. You will get a burn like a sunburn in minutes.
• Using wet gloves. Sweat-soaked leather conducts, and a shock is more likely.
• Wearing a polyester shirt under your jacket. It melts into a burn at the collar.
• Ignoring damaged cable. A worn spot can shock you or arc against the work.

Check Your Understanding

You flashed your eyes tacking a bracket at 3 p.m. You feel fine at 5 p.m. Are you in the clear?

No. Arc eye often shows up 6 to 12 hours later, so pain may hit that night. Tell your supervisor and get medical care if symptoms appear. Eye protection and a helmet for every tack prevent this.

You are MIG welding at 180 amps. What is the lowest legal shade, and where should you start?

The OSHA minimum is shade 10. Start darker, around 12, and go lighter only as far as you need to see the puddle.

It is hot, your gloves are soaked with sweat, and you need to change a stick electrode. What should you do?

Change to dry gloves first. Wet leather lowers your resistance, and the electrode holder is live whenever the machine is on.

You need to weld inside a damp steel tank. What about this job raises the shock risk?

Your body is in contact with grounded metal and moisture is present. Use insulating mats, dry gear and any voltage-reducing device, and follow the site's confined space procedure.

Key Takeaways

• Arc light burns eyes and skin, and arc eye can show up hours later.
• Pick the shade by process and amperage, starting dark and never going below the minimum.
• Cover all skin with dry, flame-resistant, non-melting clothing.
• Wear safety glasses under your helmet.
• The welding circuit can kill. Stay dry, stay insulated, and inspect your cables.
• Screen your arc so it does not burn the people around you.