Incandescent light bulb Small variations in resistivity along the filament cause "hot spots" to form at points of higher resistivity; a variation of diameter of only 1% will cause a 25% reduction in service life. These hot spots evaporate faster than the rest of the filament, which increases the resistance at that point—this creates a positive feedback that ends in the familiar tiny gap in an otherwise healthy-looking filament. Irving Langmuir found that an inert gas, instead of vacuum, would retard evaporation. General service incandescent light bulbs over about 25 watts in rating are now filled with a mixture of mostly argon and
Phase-out of incandescent light bulbs in Europe, owing to CFLs' inferior colour representation. The European Association for the Co-ordination of Consumer Representation in Standardisation (ANEC) has called for a speedy reduction of the mercury levels contained within CFLs from the current 5mg limit to 1 mg. The European Consumers' Organisation, BEUC, said that phasing out incandescent bulbs will be detrimental for people suffering light-related health issues, and called for the continued availability of incandescent bulbs: The EU Regulation falls short of the needs of some consumers who need to use the old-style light bulbs for health-related reasons such as light sensitivity. We call on the