Precious old books are being aired out at Japan's oldest school. The institution is located in Tochigi Prefecture, which is north of Tokyo.

More than 17,000 books are housed at Ashikaga Gakko in Ashikaga City. Among them are books that are hundreds of years old. Some of them have been designated as national treasures or national important cultural assets.

Every year during this season, the city's staff members air out the books to protect them from bugs and mold.

On Thursday, the staff members moved 53 books from the library to a room. They exposed the books to fresh air and spread them out on the tatami floor. Among the 53 were books about the art of war from ancient China.

The staff members wore face masks and gloves. They carefully turned the pages one by one to expose them to dry air. They also checked the pages and the binding cords to see if any damage had occurred.

The city says the work will continue through early November. Officials note that it will be done mainly on sunny and dry days. The city also says that visitors are welcome to come and watch the staff members work.

Saito Kazuyuki is the chief of the historic site's operating body. He said the annual work is one of the methods that has been used for a long time to preserve the precious books at the site. He also said that he would like many people to see how the books have been protected.