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 government departments, public sector undertakings, various boards, cooperative institutions, local bodies, and institutions running on government aid. Japan will phase out incandescent light bulbs and fluorescents by 2020. Kazakhstan banned all bulbs over 25W on 1 January 2014. As of 1 August 2017, Kuwait has banned the import of incandescent light bulbs, including halogen bulbs. It was reported in 2012 that Malaysia would ban incandescent bulbs by 2014. North Korea reportedly made LED bulbs mandatory in 2014 in order to alleviate its energy crisis. In February 2008, president Gloria Macapagal Arroyo called for a ban of incandescent light bulbs by