What Eye Protection is Required for CNC Plasma Cutting?

What Eye Protection is Required for CNC Plasma Cutting?

Eye Protection Recommendations for Plasma Arc Cutting

When it comes to welding, protecting your eyesight is an important part of it. In fact, looking at an arc can cause eye damage, including permanent problems and even blindness. This is simply because a plasma cutting arc gives off a broad spectrum of electromagnetic radiation. It extends from Infrared light (IR) through the visible spectrum and into the Ultra Violet (UV) range. Plasma cutters can also be intense because the arc current is anywhere from 100 to 800 Amperes.

Eye Protection Recommendations for Plasma Arc Cutting

There’s no eye protection required for CNC plasma cutting. However, there are several sources of recommendations, including OSHA and ANSI.

The chart from "OSHA Fact Sheet “Eye Protection Against Radiant Energy During Welding and Cutting in Shipyard Employment” also references the ANSI numbers. The protective shade numbers refer to the darkness shade of safety glasses or welding shields. The higher the number the darker the glass

ANSI and the American Welding Society (AWS) publish a slightly more detailed chart in “ANSI Z49.1:2005 Safety in Welding, Cutting, and Allied Processes.”

In both cases, the recommendations state to “start with a shade that is too dark to see the weld zone. Then, go to a lighter shade which gives a sufficient view of the weld zone without going below the minimum.”

By comparison, the ANSI recommendations for SMAW, GMAW, and FCAW welding are all in the 10 – 14 shade range.

How to Apply These Recommendations

When you’re welding, you tend to stand still and look at the weld zone through a helmet. This allows you to manually operate the welding torch just inches away from your face.

Operating a CNC plasma cutting machine is a little different in that:

  • The operator is often much farther away from the arc.
  • The operator needs to move around, so s/he must be able to clearly see the surroundings (it would be unsafe to walk around the shop under a welding helmet).
  • The operator needs to be able to see the machine control, as well as the overall machine while the arc is on.
  • The arc is moving and the operator is not always looking in that direction.

With these considerations in mind, how can a CNC plasma operator wear glasses as dark as a welder’s shield and still see enough to get anything done? There are different opinions when it comes to eye protection for CNC plasma cutting.

Obviously, if you were to operate an 800 Amp plasma torch at the same distance as a typical welding torch, you would need a welding helmet for protection. But nobody stares at the arc while operating a CNC machine unless trying to diagnose something while cutting. In that case, a welder’s shield is usually held between the face and the torch to allow safe viewing. For the normal operation of a CNC machine, though, this is too dark.

Some in the industry recommend only using protection against UV and IR light. They believe visible light can’t harm your eyes. Since most safety glasses (even clear ones) filter out UV and IR light, dark shades are not required.

However, their evidence is not definitive and not worth the risk when you’re talking about maintaining your eyesight. In fact, an increasing body of research points to intense visible light as a cause of eye damage, including macular degeneration, retinal detachment, and permanent blindness.

The source of the problem is “blue light.” Visible light includes wavelengths in the range of 380 to 780 nm. Shorter wavelengths within this spectrum create light in the “blue” range. These are the more energetic wavelengths, making them more hazardous for long-term retinal exposures.

This spectral analysis shows what the relative intensity of light across the spectrum might look like coming from a typical plasma cutting arc. The most intense, visible light is in the “blue light” range.

Since a plasma arc generates light across the entire spectrum, it definitely includes “blue light” in the light that you see. The visible light from a plasma arc is extremely intense, as is the damaging “blue light.” It is therefore potentially dangerous to the human eye.

The problem is that you can’t feel retinal damage until it’s done. If you damage your retina, the only way you’ll know is when your eyesight begins to decline. This damage is permanent.

What’s the Answer?

There is a happy medium that protects the CNC plasma operator’s eyes and still allows them to see, operate the controls, and walk around the shop without tripping. The recommended shades may be dark, but wearing safety glasses that are clear is not the answer. Wearing safety glasses with yellow lenses is recommended, instead, to block potentially damaging blue light. In addition, a secondary shield between the operator and the cutting torch, perhaps a welding curtain or dark plastic shield, can also help shade the operator from the most damaging radiation.

References for Eye Protection Required for CNC Plasma Cutting

OSHA Fact Sheet - Eye Protection against Radiant Energy during Welding and Cutting in Shipyard Employment

ANSI Z49.1:2005 Safety in Welding, Cutting, and Allied Processes

The Risk of Eye Damage from Bright and Blue Light Therapy

The Scientific Journal of The Royal College of Ophthalmologists - Retinal light toxicity