# Do CF bulbs have UV danger?
**URL:** https://boards.straightdope.com/t/do-cf-bulbs-have-uv-danger/434379
**Category:** Factual Questions
**Created:** [January 21, 2008, 3:32pm UTC](https://boards.straightdope.com/t/do-cf-bulbs-have-uv-danger/434379 "2008-01-21T15:32:42Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@The\_Controvert](https://boards.straightdope.com/u/The_Controvert)
#### Post date: [January 21, 2008, 3:32pm UTC](https://boards.straightdope.com/t/do-cf-bulbs-have-uv-danger/434379/1 "2008-01-21T15:32:42Z")
I noticed my relatively inexpensive compact fluorescent bulbs from Walmart have certain spots that do not glow. I assume this is due to inadequate coverage of the fluorescent layer. When the bulb is on, those spots appear transparent. Since CFBs emit UV light, which the fluorescent layer converts to visible light, do the transparent spots pose any danger? Or does the glass-like layer block any and all UV that might have been missed?
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### Author:  [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)
#### Post date: [January 21, 2008, 5:26pm UTC](https://boards.straightdope.com/t/do-cf-bulbs-have-uv-danger/434379/2 "2008-01-21T17:26:13Z")
[QUOTE=The Controvert]
Or does the glass-like layer block any and all UV that might have been missed?
[/QUOTE]
Not all, most likely (depending upon the particular type of glass used), but certainly most of the shortwave UV–which is the most damaging anyway. If it’s ordinary silicate glass, it’ll be largely opaque to longwave UV, too.
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### Author:  [@beowulff](https://boards.straightdope.com/u/beowulff)
#### Post date: [January 21, 2008, 6:19pm UTC](https://boards.straightdope.com/t/do-cf-bulbs-have-uv-danger/434379/3 "2008-01-21T18:19:00Z")
Like the Earth, they are “Mostly Harmless”, but I still wouldn’t use them to illuminate precious artwork. Even small amounts of UV can cause fading over long periods of time.