For six months, a special specialist has been working at Dusseldorf Airport: Zoll-Luke Luke. According to customs, the three-year-old German shepherd is currently the only cash-tracking dog trained in Germany for human controls. In the past six months, he has already sniffed out a total of 1.2 million euros in cash to passengers.

With 21 passengers, Luke indicated they carry a suspiciously large amount of cash. Because nearly every passenger has banknotes with him and Luke should only track sums of over 10,000 euros, he is trained on thicker bundles of money.

What he smells is the special combination of money printing inks and paper of banknotes. Because money stinks after all. "Each currency even smells different," says handler Sabine Mohren. Your dog is trained on Euro, US Dollars, British Pounds and Turkish Lira.

Rolf Vennenbernd / DPA

Customs dog Luke and dog handler Sabine Mohren at the airport Dusseldorf

Since 2007, more than 10,000 euros of cash have to be declared to customs when they are brought into or out of the EU. This is to complicate terrorist financing, money laundering and serious crime such as drug trafficking.