The UV radiation from an arc causes arc eye in bystanders at a distance, and spatter travels further than most people expect — a screen is a requirement wherever welding happens near other workers.
Curtains are graded by shade for flash protection, and by material for spatter resistance. Transparent vinyl curtains are used where visibility is needed — they block UV while letting light through, which is why they look orange or amber. Opaque canvas and duck curtains block light entirely and are used where visibility is not needed. Both types are treated for flame resistance, and the certification (NFPA 701, CPAI-84 and similar) is what makes them acceptable to a fire inspector.
Width, height and mounting hardware determine whether a screen actually protects. Curtains need to be hung so the arc is not visible from the sides or above; floor-mounted frames, ceiling tracks and portable screen frames each suit different shop layouts. Grommets and tie-backs keep the curtain in place rather than billowing.
Welding blankets serve a related purpose — protecting surfaces and equipment from spatter rather than blocking the arc from view.
