Can You Bring a Thermometer on a Plane?

Whether you are travelling with a sick child, managing a medical condition, or simply packing a first aid kit, knowing which thermometers are and are not allowed on planes matters. The rule is simple: almost every modern thermometer is fine to fly with. The one exception — mercury glass thermometers — is a firm, worldwide ban.

Digital Thermometers: Fully Allowed

Digital thermometers of any type are permitted in both carry-on and checked luggage with no restrictions:

• Oral digital thermometers — the standard stick-type battery-powered thermometer
• Ear (tympanic) thermometers — infrared sensors measure the eardrum; widely used for children
• Forehead (temporal artery) thermometers — scan across the forehead; popular for quick checks
• Pacifier thermometers — measure temperature orally for infants
• No-contact infrared thermometers — point-and-scan models used clinically and during screening

These contain no hazardous materials. The small batteries inside (typically AAA or coin cells) are within aviation safety thresholds. Security officers do not restrict digital thermometers, and customs authorities in virtually every country have no issue with them.

Mercury Thermometers: Banned from All Flights

Mercury thermometers are prohibited from air travel worldwide. This is not a TSA-specific rule — it is an international aviation standard set by IATA (International Air Transport Association) and enforced by national aviation authorities including the FAA (USA), EASA (EU), CAA (UK), CASA (Australia), and Transport Canada.

Why mercury is banned:

Mercury is a liquid metal that is toxic and extremely difficult to clean up in an enclosed space like an aircraft cabin. If a mercury thermometer breaks in the aircraft hold or cabin:

• Mercury vapour spreads rapidly in the enclosed, pressurised cabin environment
• Mercury corrodes aluminium, which is the primary structural material of aircraft
• Even small spills can cause significant damage to aircraft components
• Cleanup requires specialist hazmat procedures that would ground the aircraft

IATA Dangerous Goods Regulations list mercury as a forbidden item in both cargo and passenger baggage on commercial flights.

How to Tell If Your Thermometer Contains Mercury

The US largely phased out mercury clinical thermometers in the 1990s, and many countries followed. However, older thermometers — particularly those passed down in families or bought decades ago — may still contain mercury:

• Mercury thermometers have a visible silver column that rises with temperature. The substance looks like a shiny metallic liquid thread inside the glass.
• Mercury-free glass thermometers use a red, blue, or other coloured liquid (alcohol-based) or a silver-coloured gallium-indium alloy (Galinstan). These are safe to fly.
• Digital thermometers have a digital display and no liquid column at all — always safe.

If you are unsure, check the product packaging or manufacturer's documentation. If you cannot confirm mercury-free status, do not fly with it.

Mercury-Free Glass Thermometers: Allowed

Modern glass thermometers that do not contain mercury are permitted in carry-on and checked luggage. These use either:

• Alcohol (coloured dye) — a thin red or blue column, very common
• Galinstan — a gallium-indium-tin alloy that looks silver like mercury but is non-toxic

Both types are allowed. If you are unsure whether your glass thermometer is mercury-free, the packaging typically states "mercury-free" or "mercury-safe," or lists "gallium alloy" as the filling.

Fever Strips and Adhesive Forehead Thermometers

Liquid crystal fever strips (the adhesive forehead strips that change colour) are allowed without restriction. They contain no glass, no liquid in a container, and no hazardous materials. Pack as many as you need.

What About Smart or App-Connected Thermometers?

Smart thermometers (Bluetooth or Wi-Fi connected models like Kinsa or Withings Thermo) are standard digital devices and are fully allowed. They contain lithium batteries within standard aviation limits — no special declaration is required for the batteries in these devices.

Best Thermometer for Travel

For travel purposes, a digital ear or forehead thermometer is the most practical option:

• Compact and lightweight
• No glass to break
• Battery-powered, long-lasting
• Works quickly without contact (forehead models)
• Available for under $20–30 at most pharmacies

A travel-specific compact model is worth considering if your usual thermometer is bulky. Inexpensive digital oral thermometers are also perfectly functional and fit easily in a toiletry bag.

Checked Luggage Considerations

Mercury-free glass thermometers can go in checked luggage but benefit from careful packing — glass items can break under luggage pressure. Wrap in clothing or bubble wrap. Digital thermometers have no fragility concerns.

Key Takeaways

• Digital thermometers (oral, ear, forehead, temporal) are fully allowed in carry-on and checked bags
• Mercury thermometers are banned from all commercial flights — carry-on and checked luggage alike
• Mercury-free glass thermometers (alcohol or gallium-alloy filled) are allowed
• If in doubt about whether a glass thermometer contains mercury, do not fly with it
• Fever strips, adhesive strips, and smart thermometers are all allowed
• A digital ear or forehead thermometer is the best travel option — compact, reliable, and unrestricted