http://www.uvex-laservision.de/en/laser-knowledge/laser/
This is great info. It will make you think twice next time you hit fire with the lid up.
Every section here is gold, well worth reading through them.
I’m still confused on something. Is the only danger from a direct hit to my eyes or is there some kind of radiation given off from the beam or the tube that can damage my eyes?
It is the “deflection” of the beam off other surfaces. The beam is coherent and does not spread nor does it radiate energy. So if the deflection directly hits the eye, yes it can cause damage. Deflection in this case would be anywhere the beam is directed due to mirrors or other items that can deflect the beam from its intended course.
Which includes what you are lasering (if metal or shiny)… but usually that’s focused for only a little bit. Luckily (!?) for a K40 CO2 laser, the beam will not focus in your eyes (but a 40W beam will burn your lens, so don’t stick your head in there), and is reflected mainly by metals; since it’s absorbed by most things, even the plexi window of the machine is great protection.
OTOH, if you’re playing around with the 4W laser diodes (BluRay), those will hurt your retina, and UV/Blue is reflected by dang near everything (and 4mW is bad for eyes, so you only need 0.1% of the beam to hit them and your vision is permanently scarred) – use protection at all times with UV/Visable lasers (and even 1064 YAG lasers – they’re not far enough to be stopped by your lens).
OT3H, you can look at the glowing tube fine (don’t look at the ends).