Polyurethane foams — seat foam, packing foam, soft packaging foam — release hydrogen cyanide when burning and ignite instantly under the beam. It is one of the most dangerous materials to put in a laser machine.
What actually happens
The cellular structure of foam holds a lot of air: flame spreads through the volume, not just the surface, and a foam fire inside an enclosed machine becomes uncontrollable within seconds.
Burning polyurethane releases hydrogen cyanide and isocyanates. These are the gases responsible for most deaths in house fires: no workshop extraction offers sufficient protection.
What to use instead
For case or box inserts: EVA foam (cross-linked polyethylene), which cuts cleanly with a CO2, with slightly melted but neat edges.
For soft padding: knife or hot-wire cutting, outside the laser machine. PU foam has no place in a laser workshop, even in small quantities.
Every figure on LaserSettings comes with the machine, the laser source, the material and the thickness it was tested on. A setting published for a 10 W diode says nothing about a 40 W CO2, and a setting for 3 mm says nothing about 6 mm: check those four things before you copy any number.
Settings are confirmed or disputed by the members who reproduce them, so reliability comes from cross-checking rather than popularity. Photos of the result — cut edges, engraving shades, scorching — tell you more than a single number found on a forum.
Whatever the material, treat a published setting as a starting point: run a small power/speed test grid on an offcut, clean the lens, redo the focus, work with fume extraction and air assist, wear glasses rated for your wavelength and never leave the machine unattended.