Hazard Knowledge

These signs work using high-voltage electricity to excite a gas in the tubes. This gas will not always be neon; the tubes will more commonly contain argon gas with a small amount of mercury, which is a toxic substance. When energised, this creates a mercury vapour that can be released if the tube fails.

Figure 11: Luminous discharge tube ('neon') sign - photograph courtesy of Janet Guthrie

Typically, a luminous discharge tube sign will require a high voltage (such as 3kV) to start up, but the voltage is reduced once the light is working. If a luminous discharge tube breaks or goes out, this does not necessarily mean the electrical circuit is broken. Connections and 'jumper wires' between the tubes may still be live.

Also refer to the BRE knowledge sheets, Luminous discharge tube ('neon') signs.