An engraving or cutting laser concentrates several watts of light onto a spot a few hundredths of a millimetre wide. At that energy density the beam burns material in a fraction of a second: that is what produces a crisp contrast on wood or a clean cut through plywood, and it is also what makes the machine dangerous for your eyes, your skin and the air in your workshop. The rules gathered on this page do not replace your machine's manual; they collect the precautions every manufacturer repeats and that makers often learn too late.
The first risk is to your eyes. A single brief reflection can destroy retinal cells without any immediate pain. Wear filtering goggles matched to your source's wavelength (goggles for a 455 nm diode protect neither against a 10.6 µm CO2 nor against a 1064 nm fibre laser), keep the lid closed while the machine runs, and never replace a factory enclosure with an uncertified transparent panel.
The second risk is respiratory. Engraving and cutting release smoke, fine particles and sometimes irritant gases. Some materials must always be avoided: PVC and faux leather contain chlorine, which turns into compounds that corrode your lungs and your machine's mechanics; ABS and polycarbonate melt and give off acrid fumes instead of cutting cleanly. Extraction to the outside, or a properly maintained activated-carbon filter, is not a comfort accessory.
The third risk is fire. Felt, cork, thin paper and very resinous wood can ignite mid-cut. Never start a long job unattended, keep an extinguisher or fire blanket within reach, empty the debris tray regularly, and clean the honeycomb bed where residue builds up and feeds flames.
Finally, be sceptical about settings found online — including the ones published here. A power and a speed mean nothing without the exact machine, source and thickness that go with them, and two boards of the same species can behave differently depending on their moisture content. Always run a test grid on an offcut before committing a final piece: that is exactly what the LaserSettings test-grid generator was built for.