There are 3 different types of UV light
- UVA (315-400nm) is commonly known as "black light". This is fairly safe UV light.
- UVB (280-315nm) is dangerous with overdose and will cause the skin to burn and blister.
- UVC (100-280nm) is very dangerous and is mostly blocked from the sun by the earth's atmosphere .
Fluorescent lighting tubes generate UVA and the powder on the inside surface of the glass tube becomes fluorescent and glows to produce a very efficient form of lighting.
Fluorescent tubes in dance clubs have a special glass coating so only the safe part of UVA "black light" is transmitted into the room, making only some items become fluorescent and glow extra brightly.