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 media outlets and industry forums, and he was invited as one of six experts to testify before the U.S. Senate Committee on Energy and Natural Resources on 11 March 2011. CFLs, like all fluorescent lamps, contain small amounts of mercury, as both vapor and droplets inside the glass tubing, averaging 4.0 mg per bulb. The inclusion of liquid mercury is specifically prohibited from other domestic products in some jurisdictions, notably Europe. Safe cleanup of broken compact fluorescent lamps is different from cleanup of conventional broken glass or incandescent bulbs. After a proper cleanup, any potential short term exposure offers no