They are usually used to verify that a purported UVC lamp is working, rather than working as a measure of protecting your eyesight, but maybe I should start bringing one of these to any concerts I go to.
I would not rely on a stain test designed to be used in close proximity to a light source being sensitive enough to detect eye-damaging UV at a distance. It might react only slightly, and the stain may not be discernible from the control in such circumstances.
Even clear "sunglasses" made of polycarbonate can provide excellent UV protection, but no telling if it's enough to protect against a blacklit room or stage laser that's been set up by incompetents.
I'm thinking UV safety glasses too. If you attend with one of these cards, you've already been subjected to them too. At least with glasses, you can have some protection. Unless you're going to wears these over your eyes as protection
The point, I'm assuming, would be to simply leave if those things indicate there is a lot of UV present. I certainly would not hang around regardless of adequate protection.
https://www.amazon.com/QuantaDose-Light-Power-Visibility-Tec...
They are usually used to verify that a purported UVC lamp is working, rather than working as a measure of protecting your eyesight, but maybe I should start bringing one of these to any concerts I go to.