Keeping foreign money as a souvenir is common practice after traveling abroad.

According to an online survey by British flight search engine Skyscanner, of 1,000 Chinese tourists, 94.7 percent have foreign currency at home. About 70 percent of them have US dollars, 67 percent have HK dollars and more than 40 percent have euros.

Theses 1,000 tourists have money worth about 446,000 yuan ($72,740) in foreign currency. In 2012, about 80 million Chinese traveled overseas.

Extrapolating the figures would suggest that a huge sum of foreign money is in our homes.

Although most people think they will bring the money when they travel again, about one third forget about it.

“Before the next trip, one should check one's drawer and bring the useful currency. One may as well donate the foreign money to charities when the tour ends. Most airports have collection boxes,” said Bao Yi, Skyscanner's General Manager for Greater China.