Perhaps you've bought one? They usually cost $80-$150, are advertised as something like "Laser Engraver Printer Cutter Carver DIY Engraving Machine," and have names like NEJE and SuperCarver. They're quite cute, with a laser module that looks like a little laser pointer wrapped in a heat sink. However, that cute little laser is most commonly 300mW, 500mW, or 1000mW. That's plenty of power to quickly burn designs into wood -- also more than enough to cause serious injury almost immediately if used in unsafe ways.
In the US, I think many people have gotten used to the danger of low-power lasers being overstated. Looking directly into the beam from a Class IIIa laser device, such as laser pointer or laser scanner, could be hazardous to the eyes, but they are otherwise quite safe. The catch is that those devices only deliver between 1mW and 5mW. The laser in your cheap engraver might look like a laser pointer, but it delivers enough power to require very different handling to be safe.
Avoid the temptation to try things first and read instructions after a serious problem has surfaced: I didn't even plug-in my laser's power supply until after I had built an enclosure for the unit.
I'm not an expert in the law, nor in laser safety. I'm just a maker who sees the potential, both good and bad, of these little engravers. You bear all responsibility for safe configuration and operation of your laser. I'm writing this Instructable to try to make folks more aware of the potential for serious bad... and to describe what I did with the intent of reducing the risk and improving functionality. In sum, when you saw "DIY" in the advertising of these engravers, you probably wondered what was left for you to "Do It Yourself" -- the units seem fully assembled. The answer is mount the laser and add safety features.
Actually, this Instructable not only overviews the safety issues and suggests fixes, but also applies improvements that make the machine more consistent and easier to use. There are other ways it could be done, but I took advantage of 3D-printing to make custom parts upgrading the laser engraver -- and I've made my designs for those parts freely available so you can too. Never forget that you can use your tools to make better tools.
Before going into the details of how we'll make the device safer, it's useful to get a quick understanding of how much damage misuse of one of these laser engravers could cause.
You can get more gory details about what damage lasers can do from many web sites, including the wikipedia article on laser safety, the laser safety facts web site, and OSHA's guidelines. These little semiconductor lasers definitely can hurt you, but.... DON'T PANIC! Think of it this way: using these lasers is truly dangerous if they are handled incorrectly, but so is improperly using many power tools or driving a car. Use reasonable care, and everything should be fine.
By the way, the sticker design above is the label I made to warn of the danger. I know it looks scary, and your laser probably didn't come with any such sticker, but it really should have. Put an appropriate warning sticker on your unit! At least print-out and fill-in the blank sticker above. The key elements for an appropriate warning are:
It should go without saying that kids, and adults unaware of basic laser safety issues, should never be using this type of laser without supervision.