So now when I go to a place with blacklights, how do I know someone didn't get confused (or is just ignorant) and used bulbs that can burn my eyes? Thanks.
If the blacklights are LEDs they are UV-A and safe. UV-C LEDs exist, but they are so expensive noone would make a stage lighting fixture out of them.
If they are fluorescent tubes that look kinda purple, black or really deep blue when off, they are UV-A and safe. These tubes use a phosphor to convert UV-C light to UV-A light and are made of wood's glass to filter out all but that UV-A light.
If they are fluorescent tubes that are clear, they are UV-C and unsafe.
Theres a third type that uses phosphor and regular glass that emits UV-A and some white light, but those are almost never seen in stage lighting fixtures.
There are also UV-A arc lamps like the Wildfire IronArc series, which are safe as long as they have the dark purple wood's glass filter installed on them (these lamps do not ship without such a filter, but sometimes you encounter used ones that the filter was broken in or otherwise removed).
If they are fluorescent tubes that look kinda purple, black or really deep blue when off, they are UV-A and safe. These tubes use a phosphor to convert UV-C light to UV-A light and are made of wood's glass to filter out all but that UV-A light.
If they are fluorescent tubes that are clear, they are UV-C and unsafe.
Theres a third type that uses phosphor and regular glass that emits UV-A and some white light, but those are almost never seen in stage lighting fixtures.
There are also UV-A arc lamps like the Wildfire IronArc series, which are safe as long as they have the dark purple wood's glass filter installed on them (these lamps do not ship without such a filter, but sometimes you encounter used ones that the filter was broken in or otherwise removed).