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? Commented Dec 25, 2013 at 21:54
  • 1
    @AnkurBanerjee nah, not that. the mercury is the reason. Commented Dec 25, 2013 at 21:55

2 Answers 2


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.

  • 3
    Note: There are plenty of mercury-free analogue thermometers which should be fine to take on an airplane.
    – uncovery
    Commented Dec 24, 2013 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 ? Commented Dec 24, 2013 at 17:27
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    @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. Commented Dec 24, 2013 at 17:30
  • @uncovery Too bad nothing beats old mercury termometer in terms of reliability and accuracy.
    – Erbureth
    Commented Oct 14, 2014 at 8:48
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    The problem is that the mercury-aluminum reaction is catalytic. The mercury just keeps eating, it's not consumed. Commented May 25, 2015 at 22:21

Personal medical mercury thermometers in their protective case are legal for carry on or checked baggage by crew or passengers.



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