Are specific wavelength safety glasses required for closed-door (interlocked) operation?

On Amazon at least, most of the ‘laser safety glasses’, ‘10.6um safety glasses’, etc. are brandless ‘drop-shipped’ stuff; CPC/Farnell (slightly more industry supplier with a fair amount of PPE) seems not to carry any. Are they snake oil?

I have read (including on these forums) some say any safety glasses are enough, or even the window material is enough, just need some material to cut in front of your eye for long enough delay. I’m not particularly well versed in the physics - this seems to imply that nothing (of any great power anyway) can get through until it’s cut, but is this correct? Obviously visible light does, but is it really a single wavelength that’s produced, no harmonics (at lesser but not insignificant power) that might pass through?

It might be an idea to address this explicitly in the laser safety or K40 intro pages - they talk about interlocks but make no mention (whether needed or not, nevermind type) of safety glasses/goggles: Laser safety: Light and Electricity

Other comments and pages such as Sam's Laser FAQ - Carbon Dioxide Lasers suggest ‘appropriate eyewear’ or similar, without divulging what that is.

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Good thinking, we should add warnings about glasses and references to sources generally believed to be trustworthy to that page.

Here’s what I understand so far.

  • CO2 lasers are in far infrared, with wavelengths about ten times longer than visible light. What I’ve read is that 3mm of polycarbonate or acrylic is effectively opaque to those wavelengths. (Plural “wavelengths” intentional; primarily 10,600 nm but I understand also some at 9,600 nm and maybe 9,300 nm.) To the best of my understanding, any polycarbonate glasses will protect against e.g. specular reflections of CO2 laser light, for example when hitting metal. I like belt-and-suspenders when it comes to my eyes, so a polycarbonate window, polycarbonate laser goggles, and polycarbonate corrective lenses seems great to me personally! (What if an interlock switch fails?)

  • Visible and near-visible lasers (e.g. blue LED lasers) require glasses with the right dye to absorb light at the frequency the laser gives off. These I personally would buy from a reputable source. Thorlabs is an example of such a source, and I’d like to have a collection of such sources.

  • For any laser, the material being burned can produce a small spot of very intense light, with details depending on the material. At a minimum, this can include very bright near IR that is not particularly attenuated by polycarbonate or acrylic. This can, over time, “sunburn” your retina. Exactly how much probably depends on more factors than I know. I don’t know how to measure this. I do know that the retina doesn’t feel pain when it burns, so my intent is not to spend a lot of time staring directly at the beautiful bright spot…

I’d love to see here what others know. Let’s collect information and then update the into page(s) with it.


Safety glasses and window covers are NOT by themselves adequate safety protection for a machine of this laser power. You should do everything possible to protect your eyes and interlocks are simple to install.

Therefore cover interlocks should be installed and for the protection of your machine temp interlocks are also recommended.

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My question was more the opposite @donkjr - assuming interlocks are installed, thus it’s only operated with the door closed, are safety glasses necessary? And especially - do they need to be specific to the wavelength in use, or are any fine so you’re actually better off with reputable brand general purpose safety glasses than knock-off stuff with a whacky tint sold as ‘co2 laser certified 10600nm’ etc.?

I’m starting to gather perhaps the answer to the latter is it depends on the laser type - for far IR CO2 lasers any will do; diode lasers at the other end do need glasses designed for the purpose. (But nobody should take that as advice, I’m still trying to understand/find out for myself.)

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I am the Laser Safety Officer at my hospital but I am not an expert anywhere else.

Unfortunately the real answer is more complicated than it should be. There are a lot of factors that go into using laser safety shielding and glasses.

There are two standards, one for the US and one for Europe.

US standard ANSI Z-136 (with various variations Z-136.X, in particular the Z-136.1, revised in 2007)

European standard IEC 60825-1 international laser safety standard of the International Electrotechnical Commission (IEC)

You can then have additional safety regulations imposed by the state as we do here in Arizona.

Optical density ratings and total wavelength coverage can be subjective depending on the use case. It can also become expensive for the safety wear when using the more advanced ratings.

Doing a quick search for the best explanation I came across this site that has some recommendations. I do not know anything about the eyewear being recommended but they do have the correct ratings so that you can do a search and find similar eyewear if you do not trust the source. If you buy from one of the name brand laser manufactures, you will pay a premium but you will know that the product is legitimate.

Just for a quick comparison, the last eyewear I purchased for the hospital that would provide protection for three different laser systems cost $250.00 a piece.


If you have verified interlocks and operate with the door closed (never defeated) you are reasonably safe except in the unusual event the interlocks fail. That said it is good shop practice to wear safety glasses when operating any machinery so why not wear your laser safety glasses.

In this case, the glasses should be designed to attenuate at the wavelength of the laser, I would not trust general safety glasses.

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