Two different MSDS’s I’ve come across for searching for “ABS sheet MSDS” (one) (two) have varying assessments of the fire risk.
One :
5.1 Suitable extinguishing media: Water mist, dry chemical, carbon dioxide, or appropriate foam.
5.2 Extinguishing media which must not be used for safety reasons: -
5.3 Special exposure hazards arising from the substance or preparation itself, combustion products, resulting gases: During a fire, combustion products including but not limited to Carbon monoxide, Carbon dioxide, Hydrogen Cyanide, Styrene, Ethylbenzene and Acrylonitrile may be emitted.
5.4 Special protective equipment for fire-fighters: Use self-contained breathing apparatus. Use water spray to keep fire-exposed containers cool. Dust is not expected to be generated in the event of a fire.
Two (frustratingly not in actual text format; removed some of the pagination and redundant headings) :
Suspect that there are many many varieties of ABS likely to be cut in the laser, some with specific formulations, colors, coatings, whatnot that will have other considerations.
The firefighting hazards are likely specific to large quantities of the stuff going up, such as a factory, warehouse, or shipping container full. The relevance to a laser cutter will probably depend on what concentrations that small quantities of the unwanted byproducts being generated and the over/under on those compounds being released into the workshop under best/worst-case scenarios.
The effect on the lasers themselves bears consideration. What effect do these compounds have on the optics, grate, belts, etc? What’s the cleanup like if someone doesn’t adjust their cuts towards ABS seeming to prefer multiple fast low-power passes and leaves melted plastic behind?
