Which materials should you never put in a laser?

Anything chlorinated is the hard no: PVC, vinyl, and PVC-backed faux leather release chlorine gas that becomes hydrochloric acid — in your lungs and on your optics and rails. There is no safe setting for them, which is why our settings tool refuses them outright.

Also on the refuse list: polycarbonate and Lexan (fire and toxic fumes rather than a cut), ABS (cyanide-bearing and styrene fumes, melts and flares), and fiberglass or carbon fiber (burning resin plus airborne particulate). When a mystery plastic shows up, the copper-wire flame test or the trash can — never the laser bed.