Lepro Small UV Blacklight Flashlight

This one is pocket sized with a single UV emitter, for checking a note or a small area. The 51 LED version floods a wide area and is the one for searching a carpet or a mattress.

Anything that fluoresces: dried pet or human urine, many food and drink spills, some inks, security threads in banknotes and ID documents, and certain minerals. It also makes scorpions glow, which is the reason a lot of people in warmer regions own one.

Yes, the security features in modern shilling notes fluoresce under UV, as do most foreign notes and ID cards. At 395 nm you will see a violet cast over everything as well as the mark; a 365 nm light shows the mark more cleanly but costs considerably more.

Do not look into the lens, do not shine it at anyone's eyes or skin for any length of time, and keep it away from children. Short, aimed use on a surface or a document is fine.

Barely. UV inspection needs a dark room or night. Draw the curtains before you start looking for stains.

Because the organic compounds in the stain fluoresce and the fibres mostly do not. That contrast is the whole trick, and it is why a UV torch finds what a bright white light cannot.

Take the batteries out if it will sit unused for months. Alkaline cells left in anything in this climate eventually leak and corrode the contacts.