Staffers at the school's architecture library were checking in books in August when they spotted some small black dots.
"That made them look closer, and they realized there were some bedbugs in the spine of the books," said Stephanie Lamson, preservation librarian.
The bugs had crawled into the space that opens along the spine of hardcover books between the cover and the paper.
Concerned about an infestation, the staff took those books and others around them and quarantined them in plastic bags. After bugs turned up at the same library a second time that month, there were a total of about 45 potentially affected books. They de-bugged them in a natural history museum freezer.
High heat also kills bedbugs, but the library didn't want to risk damaging the books.
Since then, all of the university's libraries - there are more than a dozen - have been on the lookout for the insects, which can be difficult to eradicate. So far, no other facility has found any of the bugs.
Lamson said Friday a temperature of 18 degrees below zero killed the pests discovered in the architecture books.
The books were frozen for seven days, allowed to warm up for six days, and put back in the freezer for another week. The second dip in the deep freeze was to kill any bugs that hatched from eggs after the first chill.
"We also had a bedbug-sniffing dog come through, just to be very careful," Lamson said. "And we were cleared."
The buggy tomes had been returned to the library book drop at the College of Built Environments on the campus in Seattle.
Because of privacy protections, no record was retained to identify the patron with the pests. Lamson believes it's "someone who had an apartment or home infested and had books close to the bed probably for some time because bedbugs like small, dark contained spaces."
"They probably had a significant problem," she said.
Lamson says she is sick of bedbugs, especially after the attention the library is getting following a New York Times story. There's a very low risk of picking up bedbug at a library, she said.
"You don't need to be afraid of your library."