Will a hamster set off airport security scanners?

A hamster will not set off the security alarm, because detectors only beep on metal. But if the hamster goes through the scanner with luggage, it will be detected on the image. Under transport regulations, hamsters cannot be taken on trains, planes, or buses. Even if its small size escapes notice, once discovered it will be confiscated, and you would likely have to abandon it at the station.

So before a long trip, arrange for a friend or pet shop to care for the hamster.