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 to delay new energy efficiency standards for light bulbs until 1 January 2014, when it will become illegal to import inefficient incandescent lighting across the country. In December 2011, Ontario Energy Minister [Chris Bentley] confirmed that Ontario is scrapping the five-year-old plan "to avoid confusing consumers". The Energy Star program, in which Natural Resources Canada is a partner, in March 2008 established rules for labelling lamps that meet a set of standards for efficiency, starting time, life expectancy, colour, and consistency of performance. The intent of the program is to reduce consumer concerns about efficient light bulbs due to variable