Occupational Optics & Workplace Vision • 10 min read

Welders & Metal Fabrication: Optical Radiation, Infrared Hazards & Shade Selection

EXECUTIVE CLINICAL SUMMARY
An industrial electric welding arc burns at over 5,000°C, generating an intense plasma plume that emits violent electromagnetic radiation spanning ultraviolet (UV), blinding visible light, and invisible near-infrared (IR). We break down the clinical pathology of Photokeratitis (Arc Eye), thermal Infrared cataracts, and the exact ANSI Z87.1 Shade Number equations.
ELLASUV Clinical Metrology Laboratory Industrial Ophthalmic Safety & Radiometry Division
ISO 8980-3 / ANSI Z80.1 Metrology Updated: 2026-09-07 ✓ Peer-Reviewed

The Three Optical Killers of the Electric Welding Arc

When striking an arc in MIG, TIG, or Stick welding, the electric discharge produces three distinct destructive wavebands:

  1. Ultraviolet Radiation (200nm – 380nm): High-energy actinic UV strikes the superficial corneal epithelium, denaturing cellular nuclear DNA within seconds. 6 to 12 hours later, dead epithelial cells slough off, exposing raw corneal nerve endings. This agonizing condition is clinically termed Photokeratitis (popularly known as Welder's Flash or Arc Eye).
  2. Intense Visible Luminance (380nm – 780nm): Exceeds 10,000,000 candelas per square meter, instantly bleaching retinal photopigments and causing permanent central scotomas.
  3. Infrared Radiation (780nm – 3,000nm): Invisible thermal radiation penetrates deep into the ocular media, absorbed by the iris and crystalline lens. Over years, chronic thermal heating denatures crystallin proteins, producing Glassblower's / Welder's Cataracts.

The Mathematical Physics of Welding Shade Numbers (SS)

Under international standard ANSI Z87.1 and ISO 4850, the optical density and luminous transmittance (TLT_L) of a welding filter are governed by the logarithmic Shade Equation:

Shade Number S=1+73log10(1TL)\text{Shade Number } S = 1 + \frac{7}{3} \log_{10}\left(\frac{1}{T_L}\right)

For example, a Shade 10 lens transmits only 0.00139% of visible light, while completely extinguishing 99.999% of ultraviolet and infrared radiation.

ANSI Z87.1 Shade Selector Matrix by Welding Process

Welding Operation / ProcessCurrent Arc AmperageMinimum Protective ShadePrescription Eyewear Protocol
Torch Brazing & SolderingGas flameShade 3 – 4Prescription safety glasses with IR-absorbing green dye
Oxy-Fuel Gas CuttingHeavy plate (> 1 inch)Shade 5 – 6Side-shield prescription goggles
Shielded Metal Arc (Stick)75 – 250 AmpsShade 10 – 12Prescription insert or safety glasses worn beneath full helmet
Gas Tungsten Arc (TIG)50 – 250 AmpsShade 11 – 13Fast-switching auto-darkening helmet + ANSI Z87+ spectacles
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FREQUENTLY ASKED CLINICAL QUESTIONS

Expert Answers

What is welder's flash (arc eye) and how is it treated?
Welder's flash is severe corneal sunburn caused by exposure to intense ultraviolet radiation from a welding arc. Treatment includes antibiotic lubricating ointments, cycloplegic drops to relieve ciliary spasm, and dark rest; the corneal epithelium typically regenerates within 24 to 48 hours.
Can I wear contact lenses while welding?
Yes. The old urban legend that welding arcs melt contact lenses to the cornea is completely false. However, flying dust and sparks in fabrication shops can cause foreign-body corneal abrasions, so certified safety glasses must always be worn.
Do auto-darkening helmets protect against UV when they are clear?
Yes. High-quality auto-darkening helmets have a permanent internal UV/IR interference filter that provides continuous 100% protection up to Shade 13, even when the electronic LCD filter is in its light state (Shade 3).
Can infrared radiation from furnaces and glassblowing cause cataracts?
Yes. Chronic exposure to infrared heat without protective reflective or absorbing lenses cooks the crystallin proteins in the lens, causing posterior subcapsular 'glassblower's cataracts'.
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