What You Need to Know About the Airport Liquids Rule

Travelers flying in the United States need to know the rules for bringing liquids through airport security. The Transportation Security Administration (TSA) has a liquid limit rule that is known internationally as "3-1-1."

Under the rule, liquids, gels, and creams in a carry-on bag must be in containers no larger than 3.4 ounces (100 mL). All of these containers must fit in a single clear, quart-sized bag. Larger liquids must be packed in checked luggage.

The rule covers a group of items that are technically called LAGs, which stands for liquids, aerosols, and gels. This category includes creams and pastes, such as toothpaste, hairspray, and peanut butter. The TSA first introduced the rule in August 2006.

The rule has a connection to a past security event. British police foiled a plot to detonate explosive liquid in soda cans on flights from London to the US and Canada.

Rules can differ in other countries. Some UK airports, including London Heathrow (LHR), allow liquids of up to 2 liters (about 67.6 ounces). A TSA spokesperson expects the limit on liquids to be lifted in the coming years. For now, the 3-1-1 limit remains in effect nationwide in the US, because new scanners roll out differently by terminal.

There are some exceptions. The TSA allows travelers to take 10 common full-size liquids through US airport security. Travelers must declare oversized approved liquids to a security officer before screening and place them in a separate bin. Prescription medication is also an exception to the 3-1-1 rule. The TSA allows reasonable quantities of medically necessary liquids, such as inhalers, insulin, and nebulizer liquid, if they are declared to officers. Breast milk and infant formula are permitted as medically necessary liquids, and the child does not need to be present. Baby and toddler food and drinks, including juices and puree pouches, are also allowed.

Some items are treated differently. Prescription wet pet food does not count as an exception and must follow the 3-1-1 rule, even for service animals. Contact lens solutions containing chemicals that typically alarm may not be permitted through the checkpoint. Gel ice and freezer packs are permitted through security. Frozen water bottles are allowed if they are frozen solid when passing through security. Any partially melted or slushy portion of an ice pack counts toward the 3-1-1 limit, except medically necessary gel ice packs.

Other items are also allowed. Non-spillable wet batteries are permitted if the voltage is 12 volts or less and under 100 watt hours, with no more than two spare batteries. Fresh eggs, including liquid yolks, can be taken through security without following the 3-1-1 rule.