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Why do airlines prohibit carrying conventional mercury thermometers onboard? What potential this small device has to prohibit it?

PS: I prefer conventional thermometers in my personal first aid kit over electric ones because they do not need batteries and they are accurate.

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I can imagine that a glass thermometer can be broken and then used as a weapon on board. Maybe that's why? –  Ankur Banerjee Dec 25 '13 at 21:54
@AnkurBanerjee nah, not that. the mercury is the reason. –  user1712 Dec 25 '13 at 21:55
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1 Answer

up vote 11 down vote accepted

The problem isn't the Thermometer bit, it's the mercury bit. Mercury and Aluminium really don't play well together. Well, depending on your point of view, you might say they play excellently together, but the outcome is you destroy the structure and strength of your aluminium.

The problem with this is that much of the plane (including the fuselage) is made of aluminium, so having it be eaten away by mercury is a bad thing during the flight, and also a very bad thing for the value of the plane afterwards!

If you've not seen the effect of a drop of mercury on some aluminium, I'd very much suggest looking on youtube for a video, it's very quick and very noticable... This article has more on the chemistry behind it, as well as a video demonstration.

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Note: There are plenty of mercury-free analogue thermometers which should be fine to take on an airplane. –  uncovery Dec 24 '13 at 10:56
I would question the damage from the minute quantities of mercury in a thermometer. How much mercury could be possible on board even if all passengers carry one such thermometer each ? –  happybuddha Dec 24 '13 at 17:27
@happybuddha a very small amount of mercury if found its way through the floor and reached the fuselage can make a hole which could lead to slow decompression in long flights. You know, better safe than sorry. –  user1712 Dec 24 '13 at 17:30
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