We just bought a green laser pointer on Ebay and had a discussion about the safety. The laser is low end chinese one (5 USD, free shipping 🙂 ) and the seller says this:
Green Laser Pointer Point Pen
532nm
Output power: 5mW (Class IIIb)
the most confusion comes from the "Class IIIB" which, according to Wikipedia should be not safe for common use because it can damage eye even with accidential look or reflection.
However, directly on the pointer is this:
Max power output less than 5mW
Wavelegnth 532nm
Class III laser product
This product complies with 21 CFR 1040
so this looks that it should not be Class IIIB, also because the power is less than 5mW while according to Wikipedia the "B" class should be for 5-200 mW.
I also have a couple of small red keychain lasers which all are the same power output and class.
I do not intend to shine anybody in the eyes but my sister was afraid that there could be potential risk to damage someones eyes with accidential quick exposure (reflection from window in a class or directly from the chalkboard to the class). The green pointer seems to have very intensive light compared to the red ones but it could be a subjective impression caused by the different color.
I think there is rather an incorrect information on the selling page and that the pointer should be safe but I am rather asking to be sure.
thanks
Best Answer
First and foremost, you should know that the legal restrictions on laser pointers are not enforced. Therefore you should not assume the class labelling is correct. One study found that 90% of green lasers in the US had an illegally high power level.
You also should not assume the power rating is correct. It says 5mW probably because that's the most desired power level that consumers want: As bright as possible without being obviously illegal. But really it could be 2mW, or 10mW, or who knows.
Every laser pointer is dangerous, is not a toy, and should not be pointed anywhere close to other people ...but it takes extreme and unusual bad luck to cause permanent eye damage if its labeling is correct and it is really under 5mW (Note: I am talking specifically about visible-light, continuous-wave green lasers here). Here is a literature review, and you'll see that some injuries were indeed caused by laser pointers with less than 5mW of power, but most were injured by much more powerful lasers, like 30mW and higher.
Best is to find, buy, or borrow a light power meter. They're not expensive, and they're fun to have anyway.
Finally, stepping back, the review cited above found 111 patients with eye injuries from green laser pointers. Given how many green laser pointers are around, I wouldn't consider owning a legally-compliant green laser pointer to be a notably risky activity, compared to other day-to-day risks.
Owning a super-bright one (e.g. 30mW or higher) is something I would consider awfully risky. Treat a super-bright green laser pointer just like you would treat a circular saw: You store it well out of reach of children (and out of reach of irresponsible adults!), you leave it unplugged / remove the batteries when it's not in use, you don't use it if you're drunk, you don't have fun with it, etc. etc. etc.