I can not imply enough that laser safety is of the utmost importance. You will not tear through the space time continuum ( I have tried ), however, there are dangers that come with laser usage that we must acknowledge and accept. I will use the term "marking" when referring to laser marking or cutting. First, we need to accept the fact that when we laser mark or cut something, we are vaporizing that product and fumes are created. Some of them really are pretty harmless and just leave an unpleasant taste/odor in our mouths and/or noses at most. Steel and aluminum fumes generally do not have any poisonous attributes when they are hit with a laser unless in very high concentrations of the fume. Some products, especially those that are protectively coated or are a resin/chemical base, are very dangerous to us when marked with a laser. PCV, PETG and many other types of similar material produce very toxic fumes and should be avoided at all cost unless you have a sealed container system and can extract those toxins. MDF, which is commonly laser cut, creates formaldehyde fumes, which, of course are very toxic. The best option is to have a sufficient fume extractor to remove these odors/gases very near the marking area. A shop vac will not be sufficient enough as it does not have microbial and/or charcoal based filtering. Also remember, it is a fume extactor.....not a moisture extractor or debris extractor. If a quality fume extractor is not in your budget and you insist on marking toxic materials, some sort of exhaust fan drawing the fumes away and outside to an area where it will not bother other people, wildlife or plants is a minimum. Second, we need to also accept the fact that we can not see the laser, contrary to science fiction movies. A laser beam can bounce and if the conditions are just right, remain in focus or near enough focus to cause problems in the work area. It is highly recommended that a laser be ran in a Class 1 enclosure system. However, I have come across many people that run them right out in the open ( Class 4 ). Some systems due to their size have no choice but to run as a Class 4. The laser beam can be reflected onto a wall, other projects, computer screens, etc. and cause all kinds of issues we do not want. Even worse is that is can be reflected back to us. We will not explode into a ball of flames or look like we were standing ground zero on a nuclear weapons test. However, we can experience some burning of the skin or even worse, damage/loss of vision if it gets into our eyes. If you have/choose to run your laser in a Class 4 state, safety glasses are an absolute necessity. Another problem with beam reflection many people do not think about is the beam bouncing back up into the laser and ruining expensive components. Many small scale and home builders do not include a filter lens ( think of it as a diode for the laser beam ) to block incoming laser beam. We also need to understand how the 2 most common types of lasers react when hitting human flesh. CO2 ( 10600nm ): Affects the exact surface it is focused on. For an example, if you were to mark your arm with a CO2 laser, it will mark the outermost portion of your flesh. It will feel like a good burning scratch and you would see a nice white mark there ( it also hurts like hell ). There is no bleeding as it has been cauterized instantly. Diode Pump ( 1064nm ): This is different than the CO2 in that it likes to pass through flesh. For an example, if you were to run your arm under a Diode Pumped beam, you would feel nothing. There would be no mark. However, if you were to hold your arm under the beam for a few seconds, you will find a whole new meaning to the term " Burns like hell! "......but, from the inside. This wavelength will pass through soft tissue and start cooking when it hits something hard.....like a bone in your arm. This is why simply closing your eyes while marking with a Diode Pumped beam is not safe. The beam will literally pass through your eyelids and burn the optic nerves in your eyes. Hope this helps!