> The lamps were primarily used for public and residential lighting.

> Only ca. 20% of the lamp output consisted of UV(A) at 365 nm – hence the need for a UV(A) filter to remove both the white light components and also harmful UV(B) and UV(C

> A significant amount of energy was wasted as heat.

> The lamp required a ballast to regulate the voltage/current supplied to the lamp during start up and operation

> The UV output dropped with continued use.

> There were issues with disposal of the bulbs on account of the mercury content