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 products. The new minimum standard efficiency level is 15 lumens per watt (lm/W). From November 2008, no non-compliant lighting (including some incandescent globes) were imported into Australia, and from November 2009, the retail sale of non-compliant lighting was banned. According to the current proposal, all regular light bulbs and some other kinds of light bulbs sold from October 2009 have to meet the new minimum energy performance standards. Incandescent light bulbs that meet the new standards, for example high-efficiency halogen bulbs, continue to be available. It is estimated that greenhouse gas emissions will be cut by 800,000 tonnes (Australia's current