# What causes a fluorescent bulb to fail?

**URL:** <https://boards.straightdope.com/t/what-causes-a-fluorescent-bulb-to-fail/420433>\
**Category:** Factual Questions\
**Created:** [September 25, 2007, 3:56pm UTC](https://boards.straightdope.com/t/what-causes-a-fluorescent-bulb-to-fail/420433 "2007-09-25T15:56:14Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\
**Post date:** [September 25, 2007, 3:56pm UTC](https://boards.straightdope.com/t/what-causes-a-fluorescent-bulb-to-fail/420433/1 "2007-09-25T15:56:14Z")

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When an incandescent light bulb fails, my understanding is that the filament has finally, and literally, burned out and ceases to complete the circuit. What fails in a fluorescent bulb when they “burn out”?

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**Author:** ![Jas09](https://avatars.discourse-cdn.com/v4/letter/j/d07c76/32.png) [@Jas09](https://boards.straightdope.com/u/Jas09)\
**Post date:** [September 25, 2007, 4:17pm UTC](https://boards.straightdope.com/t/what-causes-a-fluorescent-bulb-to-fail/420433/2 "2007-09-25T16:17:16Z")

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> **[Fluorescent lamp](https://en.wikipedia.org/wiki/Fluorescent_lamp#Mechanisms_of_lamp_failure_at_end_of_life)**
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> A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow. A fluorescent lamp converts electrical energy into useful light much more efficiently than an incandescent lamp. The typical luminous efficacy of fluorescent lighting systems is 50–100 lum...

I’m not sure which failure mode is most common.

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**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\
**Post date:** [September 25, 2007, 4:18pm UTC](https://boards.straightdope.com/t/what-causes-a-fluorescent-bulb-to-fail/420433/3 "2007-09-25T16:18:04Z")

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N/M…scooped.

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**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\
**Post date:** [September 25, 2007, 4:18pm UTC](https://boards.straightdope.com/t/what-causes-a-fluorescent-bulb-to-fail/420433/4 "2007-09-25T16:18:44Z")

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Cool, thanks!