What substrates should I stay away from when engraving with a CO2 laser?

Substrates to stay away from processing on a CO2 laser include fiberglass reinforced plastic (RFP) and carbon fiber. Plastics that have chlorine such as polyvinyl chloride (PVC) and vinyl should never be cut (or engraved) with a laser. The thermal cutting process produces hydrochloric acid, a harmful, toxic chlorine gas fume that could potentially damage your laser, as well as is harmful to inhale.

   —Just My Imagination DeZigns