A quarantine detector dog is trained to sniff out any agricultural materials that people have when they come into the country.

Mostly they work at airports, but some work at the mail centre, where they check letters and parcels.

They are usually beagles, because beagles are small dogs, and don't frighten people. They have a very good sense of smell.

They work on a lead, with their handler, and when they can smell something suspicious, they sit down beside it. The handler knows that means that they can smell something, and they will ask the person to open their luggage.

At the airport, they run over the bags on the luggage carousel, sniffing as they run.