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 CFLs, and banned the sale and import of them in 2006–07. California will phase out the use of incandescent bulbs by 2018. The bill aims to establish a minimum standard of twenty-five lumens per watt by 2013 and sixty lumens per watt by 2018. In Connecticut legislation was proposed. A bill was introduced in New Jersey in 2007 that calls for the state to eliminate incandescent bulbs in government buildings over the next three years. In Utah energy efficiency standards for government buildings were passed in 1999 that, in practice, require the adoption of energy efficient technology, including LEDs, as