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 and sale of incandescent bulbs since December 2015. Ecuador has banned incandescent bulbs. As part of its electricity conservation program, Venezuela has a light bulb exchange program, which aims to replace millions of incandescent bulbs with compact fluorescents. The phase out has been referred to as "light bulb socialism". The consumer preference for light bulbs in the EU is for incandescent bulbs, with many complaining about what was described as the ugliness or the cold, flat, unnatural, dull light emanating from CFLs. Objection has also been raised to being forced to adopt CFLs. Bulk purchasing of incandescent bulbs was reported