Optical radiation transmission levels through 25 transparent welding curtains were determined. The curtains were made from polyvinyl- chloride (9002862) plastic film, with a color dye, a flame retardant chemical, and an ultraviolet absorber. Spectral transmittance of yellow, green, gray, or blue transparent curtains from five manufacturers was measured with a recording spectrometer. Wavelengths less than about 340 nanograms were greatly suppressed in almost every curtain tested. Optical density, curtain thickness and color influenced results. Most transparent curtains offered adequate protection from ultraviolet radiation, but not from infrared radiation. The authors conclude more work needs to be done on reflective characteristics of opaque curtains.