PTFE, known as Teflon, must not be engraved or cut with a laser. When heated it releases some of the most aggressive fluorinated compounds you can produce in a workshop.
What actually happens
Under the beam PTFE decomposes and releases hydrofluoric acid and other fluorinated compounds. Hydrofluoric acid is dangerous at very low concentrations and attacks tissue in depth, including through skin.
These compounds also attack glass: they degrade your machine's lens and window, which is specific to fluorine compared with other plastics.
No domestic carbon filter captures these gases. There is no "careful" setting: the decomposition itself is the problem.
How to recognise it and what to use instead
PTFE is milky white, very slippery to the touch, flexible but not elastic, and nothing sticks to it — not glue, ink or tape. You find it as sheets, gaskets, plumbing seal tape and non-stick coatings.
Other fluoropolymers (PVDF, FEP, PFA, ETFE) raise the same problem and must also be excluded.
For a slippery or technical part, Delrin (POM) and polypropylene cut safely with a laser. For a non-stick part, prefer machining or blade cutting: PTFE cuts very well with a knife.
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.