Any recommendations for eye protection for a new K40 user? I still haven’t so much as plugged it in, and while I do plan on always having the lid shut while operating it, I would still like to have proper eye protection (read: laser safety glasses that block the wavelength this laser emits).
Amazon has some. Need to be certified for 10600nm which is the CO2 laser spectrum. Regular safety glasses made of acrylic will defract (the window in the lid is acrylic) but won’t stop the beam from boiling your eyeball 
@Jim_Hatch Thanks! Any links to possible candidate eyewear?
Second to getting the proper glasses. Add interlocks to the doors including the back door.
Go to http://lightobject.com. they have the glasses you need. They run about $35.00.
yeah, they sell them through Amazon too. Also someone said the same glasses are cheaper through ebay from another seller.
I got these: https://www.amazon.com/gp/product/B000HJMS4A/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
And these: https://www.amazon.com/gp/product/B00L2SU1TY/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
I prefer the fit of the first ones. Make sure whatever you get provide some side protection as well as just the fronts.
@Dan_Stuettgen @Jim_Hatch Thanks! I’ll check those out.