In tests carried out in connection with market surveillance, several lamps failed to meet their required class of enclosure against harmful water penetration. Many lamps classified as IPX4 (splashproof) failed the tests as water entered the lamp, even though the lamps had no drain holes, meaning that water must be kept from entering the lamp.

The enclosure class is determined with a standardised test method. For example, in the IPX4 test, the lamp is mounted on a rotating stand, and water is splashed at it from all directions. At the beginning of the test, the lamp is on, and it is switched off halfway through the test. The test on the lamp’s sealing is quite demanding. As the lamp cools down, a vacuum may easily form inside it, which can cause water to be absorbed into the lamp, even if it would not enter a cold lamp when immersed under water, for example.