The short answer: The welding arc emits intense ultraviolet and infrared radiation that burns the cornea ("arc eye"/photokeratitis) of welders and bystanders alike. The primary control is the correct filter shade for the process and amperage — OSHA's tables in 1910.133 and 1910.252(b) give the minimums (roughly shade 7–14 for arc welding), with AWS F2.2 offering a comfort shade. About 2,000 U.S. workers a day sustain a job-related eye injury requiring treatment, and welding is a leading contributor.
Why the arc is a radiation hazard
An electric arc is a broadband source of ultraviolet, visible, and infrared radiation. Overexposure to the UV causes photokeratitis — "welder's flash" or "arc eye" — a painful inflammation of the cornea that characteristically appears hours after the exposure, long after the welder has stopped. Repeated infrared exposure is associated with cataract risk. Critically, this hazard does not require you to be the one welding: anyone in line of sight of an unshielded arc is exposed.
Selecting the filter shade
OSHA provides two references. The general eye-protection standard 1910.133 (Table I-1) gives minimum protective shade ranges by operation, and the welding standard 1910.252(b) gives a table keyed to electrode size. As a working guide for the common arc processes:
- Shielded metal arc welding (SMAW): minimum shade around 7 below 60 A, rising through 10 and up to 14 at the highest currents.
- Gas metal arc / flux-cored (GMAW/FCAW): roughly shade 7–10 minimum by current, with higher comfort shades recommended.
- Gas tungsten arc welding (GTAW/TIG): roughly shade 8–10 minimum by current.
- Carbon arc welding: shade 14. Plasma and air-carbon-arc cutting: roughly 8–11.
- Oxy-fuel gas cutting/welding: shade 3–6; torch brazing shade 3; soldering shade 2.
These are minimums. The practical method OSHA and AWS F2.2 both endorse is to start with a shade too dark to see the weld zone, then step to a lighter shade that still gives adequate protection — never below the minimum for the operation.
Protect the bystanders, too
Because the arc injures anyone who can see it, welding screens and curtains around the work are a required engineering control, not a courtesy. Under the helmet, the welder still needs impact-rated safety glasses (to ANSI Z87.1) for chipping and grinding, plus skin cover and a cap against the UV.
Auto-darkening helmets
An auto-darkening filter (ADF) switches from a light state to the selected dark shade in milliseconds when the arc strikes, and holds a protective base shade even when powered off. Quality is described by the European EN 379 four-digit optical code — optical class, light diffusion, luminous-transmittance variation, and angle dependence — each rated 1 (best) to 3. A 1/1/1/1 filter is top optical quality. Choose an ADF rated for your amperage range and verify it meets the recognized switching and optical requirements.
