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 ahead of the EU lightbulb ban. Many retailers in Britain, Poland, Austria, Germany and Hungary have reported bulk purchasing, and in Germany, sales rose by up to 150% in 2009 in comparison to 2008. Two-thirds of Austrians surveyed stated they believe the phase-out to be "nonsensical", with 53.6% believing their health to be at risk of mercury poisoning. 72% of Americans believe the government has no right to dictate which light bulb they may use. The Czech Republic President, Vaclav Klaus, urged people to stockpile enough incandescent bulbs to last their lifetime. Museums and individuals have been stockpiling incandescent lightbulbs