Are double glazing windows really sealed?

Are they air tight? I mean, even after several years they still don't get misted up inside, but I can't imagine how (with all the cold and warm contractions and expansion) they ever manage not to leak somehow? Am I missing some kind of magic here?
TIA!
Dean
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dean wrote:

No, you're not missing anything except more exposure (time) with the windows. They don't last forever. If the seal fails, you'll get fogging on the inside of the glass. The sealed units are usually warrantied for five or ten years, although it is not unusual for sealed units to last for twice that or more.
R
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dean wrote:

Yeah you are? You've missed trying to take the panes apart. Suggest you try. They will leak eventually, but sliders should last 15 or more years. The old non movable Thermopane windows easily last more than 35 years.
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They are air tight for a long time plus they have a drying agent in them to suck up moisture for a while if they do leak.

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If, or rather when they do fog up, here is someone that can fix them without having to replace the sealed window unit.
http://www.ccwwi.com /
Per

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