Ten out of 28 light bulbs tested by the Consumer Council showed signs of defects that could lead to them becoming detached from their caps and falling from lamps.
A safety performance test on the 28 bulbs showed seven of them became detached from the metal caps or broke as they approached the end of their lives. Three others underperformed in a heat treatment test.
Since 1997, the council has received 37 complaints of light bulbs suddenly falling out of their holders due to loosened or detached glass shells. There have been no casualties.
Consumers were warned to read instructions on the wattage and limitations on types of use before installing light bulbs.
Consumer Council spokesman Larry Kwok said: 'Some bulbs should only be used in the 'cap up' position and some only in the 'cap down' position.'
Mounting some bulbs with the metal cap facing upwards could lead to excessive heating and risk damage to the bulb, he said.
