Can you take a thermometer on a plane? Rules by country

Thermometers on flights in and from Japan

The rule for thermometers comes from the Civil Aviation Bureau's list of restricted items and is the same on domestic and international flights.

Thermometer: carry-on and checked baggage in Japan
Where	Allowed?	What applies
In the cabin	Yes, within limits	Digital thermometer: yes, it is an ordinary battery device. Mercury medical thermometer: no, not in the cabin.
In checked baggage	Conditions	Digital: yes. Mercury medical thermometer: one per person, for your own use, in its protective case.

This is the reverse of what many travellers expect: the mercury thermometer travels in the checked bag, not with you.

Mercury or digital: how to tell, and where each one travels

The answer depends on what is inside the glass. Every authority here that names the mercury thermometer sends it to the checked bag.

Telling mercury from the rest: The TSA gives a quick test: thermometers with a red line instead of silver are not mercury and are not restricted. Its entry is headed Medical-Clinical Thermometer (Mercury) and allows 1 small one per passenger, for personal use, in a checked bag only. Japan's row is named the same way, mercury medical thermometer, with 1 per person in a protective case.
Digital thermometers are a battery question: Japan's list has no row for digital thermometers. What it covers is the cell inside: dry batteries and nickel-metal hydride batteries are marked as non-dangerous goods, fine in either bag, and a portable device with a lithium metal battery of 2 g lithium content or less is allowed in both as well.
A weather thermometer or barometer is another row: A mercury thermometer that is not a medical one falls under a different row. Japan's list allows mercury barometers and mercury thermometers in carry-on only, and only when staff of the Meteorological Agency or an equivalent body carry them. The TSA and CASA have a matching entry for a representative of a government weather bureau or agency, in carry-on only; CASA adds airline approval.

Thermometers: the rule country by country

The carry-on answer for thermometers is the same in all 5 other places we checked. The limits themselves are not identical, so read the row for the country you fly from.

Thermometer: carry-on and checked baggage rules by country
Flying from	Carry-on	Checked bag	What the authority says
JapanCivil Aviation Bureau	With limits	With limits	Digital thermometer: yes, it is an ordinary battery device. Mercury medical thermometer: no, not in the cabin. Source
United StatesTSA	With limits	With limits	A mercury medical thermometer is not allowed in carry-on; one small one per passenger may go in a checked bag only, in a protective case. Non-mercury and digital thermometers are not restricted, unless a digital one uses lithium batteries.TSA entry: Medical-Clinical Thermometer (Mercury) Source
TaiwanCivil Aviation Administration	With limits	With limits	A small medical or clinical thermometer containing mercury may not go in hand baggage; 1 per person may be checked, in a protective case. Source
Hong KongCivil Aviation Department	With limits	With limits	A medical or clinical thermometer containing mercury is not allowed in carry-on; one per person may go in checked baggage, in a protective case. battery-powered equipment is allowed in both. Source
Mainland ChinaCAAC	With limits	With limits	Electronic thermometer with a lithium battery of 100Wh or less, or 2 grams of lithium or less: carry-on and checked. Mercury thermometer: not in carry-on; checked only, in a protective case, one per passenger. Source
AustraliaHome Affairs, CASA	With limits	With limits	Mercury medical or clinical thermometers: checked baggage only, no more than one per person, for personal use, in its protective case. Battery-powered devices such as digital thermometers can be carried on or checked in.CASA Pack Right entry: Medical or clinical thermometers containing mercury, Batteries - dry cell (in equipment) Source

Each row comes from that authority's own page. Airlines can be stricter, and the screening officer has the final say.

If security in Japan will not let thermometers through

What to do: Move thermometers to the bag you check in before you reach security, within the checked-baggage limits above. Narita Airport states that anything given up at the checkpoint is discarded and cannot be returned.

Frequently asked questions

Can you take a thermometer on a plane?

On flights in and from Japan: Digital thermometer: yes, it is an ordinary battery device. Mercury medical thermometer: no, not in the cabin. In checked baggage: Digital: yes. Mercury medical thermometer: one per person, for your own use, in its protective case.

Can you bring a digital thermometer on a plane?

Yes. The TSA says digital thermometers are not restricted unless they are powered by lithium batteries, and CAAC allows an electronic thermometer both carried on and checked when its lithium battery is 100Wh or less, or holds 2 grams of lithium or less. CASA treats dry cell batteries in equipment as allowed in both, with the device switched off.

Is a mercury blood pressure monitor allowed like a mercury thermometer?

No. Japan's list marks mercury blood pressure monitors as not allowed in carry-on or checked baggage, the same answer it gives for mercury itself. Its exception for a traveller's own use is the medical thermometer: 1 per person, in a protective case, in checked baggage. CASA likewise marks mercury contained in articles other than thermometers as an item not permitted.

Does the TSA allow a thermometer in carry-on bags?

A mercury medical thermometer is not allowed in carry-on; one small one per passenger may go in a checked bag only, in a protective case. Non-mercury and digital thermometers are not restricted, unless a digital one uses lithium batteries.

Can you put a thermometer in checked luggage?

Digital: yes. Mercury medical thermometer: one per person, for your own use, in its protective case.

What is the rule for thermometers on flights from Taiwan, Hong Kong and Mainland China?

Taiwan: A small medical or clinical thermometer containing mercury may not go in hand baggage; 1 per person may be checked, in a protective case. Hong Kong: A medical or clinical thermometer containing mercury is not allowed in carry-on; one per person may go in checked baggage, in a protective case. battery-powered equipment is allowed in both. Mainland China: Electronic thermometer with a lithium battery of 100Wh or less, or 2 grams of lithium or less: carry-on and checked. Mercury thermometer: not in carry-on; checked only, in a protective case, one per passenger.

Related items

Sources for this page

Japan Civil Aviation Bureau (MLIT) — Items restricted in carry-on and checked baggage (updated 24 April 2026)checked October 2, 2026
TSA — What Can I Bring?: Medical-Clinical Thermometer (Mercury)checked October 1, 2026
Taiwan CAA — Dangerous goods passengers and crew may carrychecked October 1, 2026
Civil Aviation Department (Hong Kong) — Packing Tips for Air Passenger: Provisions for Dangerous Goods Carried by Passenger and Crewchecked October 1, 2026
CAAC — Air travel basics (航空旅行常识)checked October 1, 2026
CASA — Pack Right: Medical or clinical thermometers containing mercurychecked October 1, 2026