[elihu]

I have a laser cutter and I was surprised as well that it doesn't generally catch things on fire. It cuts through cardboard like it's not even there. It's only harder materials like wood that you get any noticeable flame at all, and that problem largely goes away if you use an air compressor (which also serves to blow smoke out of the way of the beam).

That said, it's always a good idea to keep an eye on the machine while it's running.