text: are carbon dioxide (co2) lasers safe? how can i build a mini-co2 lasre myself? (show me a schema)?   how safe they are depends on how powerful they are. they radiate in the infrared so the light isn't visible.   you'll need a tube with electrodes spaced apart a few feet with wires coming in. you'll need a high voltage source, maybe a transformer from a neon light hooked to the wires.   you'll need a vacuum pump and you'll need to pump the tube down to about 5 mm of pressure while you feed in a mixture of helium, neon and carbon dioxide. you'll have to look up the mixing ratio.  you'll need something to seal the end of the tube with. ideally you'll have mirrors but more than likely the mirrors will be external. one will have to be reflective the other should half silvered and of a type that won't absorb the infrared light. most glass will absorb the light and you won't get any output. some plastics work and you can always put the mirrors outside the tube  (one with a pin-hole in it) and use brewster angles (look it up) to seal the end of the tube... no glass on the seals; special plastics or sodium chloride plates work.   then you'll need an infrared detector; the light is invisible and a lot of patience aligning the mirrors.