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 light bulbs in September 2018. The provincial government of Nova Scotia stated in February 2007 that it would like to move towards preventing the sale of incandescent light bulbs in the province. In April 2007, Ontario's Minister of Energy Dwight Duncan announced the provincial government's intention to ban the sale of incandescent light bulbs by 2012. Later in April, the federal government announced that it would ban the sale of inefficient incandescent light bulbs nationwide by 2012 as part of a plan to cut down on emissions of greenhouse gases. On 9 Nov 2011, the federal government approved a proposal