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 and the United States, Canada, Mexico, Malaysia and South Korea in 2014. Objections to replacement of incandescent lamps for general lighting mainly include the higher purchasing expense of alternative light bulbs. To mitigate the cost effects of these concerns, various programs have been put in place ranging from subsidies for lamps to improved standards for measurement of performance and for labelling products. Manufacturers develop fluorescent lamps with reduced mercury content compared to original designs, and recycling programs are intended to prevent mercury release. New lamp types offer improved starting characteristics, and dimmable types are available. The light from an incandescent