So I found this multi-tool thing in my drawer, recently, which has:

  • A magnifying glass, allowed on-board, I think.
  • A compass, also OK.
  • and a thermometer, not OK.

However, the thermometer is covered in plastic very tightly and the liquid is red (mercury isn't red, is it?), so would that be OK on a plane? I don't need it, I am just curious if it is allowed and if there is anything I can do...

  • Well, not really, as I did explain that the liquid is wrapped in plastic, and is built into the tool, and the liquid might not be mercury... May 25, 2015 at 21:42
  • 2
    Explaining that to the TSA won't go well, I suspect. Thermometers are not allowed, trying to justify a different material / liquid build won't work - they're not expected to be scientists and know about liquids, just to ban thermometers.
    – Mark Mayo
    May 25, 2015 at 22:05
  • 2
    Are themometers banned by TSA? I can't find any reference to such a ban on their site. I've had a mini thermometer on my jacket for years and have never been questioned about it by TSA. The FAA specifically allows a "Small personal mercury thermometer in a protective case"
    – Johnny
    May 25, 2015 at 22:30
  • @Johnny actually it is allowed, use the "Can I bring My...?" tool in this page... May 25, 2015 at 23:13
  • Not sure it's a duplicate since this question is not about mercury thermometers. Voting to reopen.
    – JoErNanO
    May 26, 2015 at 14:30

1 Answer 1


If the liquid is red, it's mostly likely alcohol (ethanol), not mercury (so less of an issue- even if it broke it would be no worse than spilling a few drops of wine). Even small mercury thermometers are specifically allowed, as Johnny says:

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By the TSA and some other authorities (but Cathay Pacific, for example, does not allow them).

So I think it should be okay, but you never know- you might lose it if some overzealous agent deems it a danger.

  • OK. Thanks. I didn't take it just in case but I will next time. Jun 13, 2015 at 16:35

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