The same qualities that make libraries ideal for studying and reading – unfettered public access, quiet corners and nooks, minimal interaction with other people – also make them appealing places to shoot up heroin, librarians are finding.

In Norfolk, Virginia, a 47-year-old man died after a patron found him in a library restroom. In Batesville, Indiana, and New Brunswick, New Jersey, police revived others in library restrooms using an overdose antidote.

The body of a homeless man who frequented the Oak Park Public Library outside Chicago might have been there for days, slumped on the toilet in a restroom on the quiet third floor, before a maintenance worker unlocked it on a Monday in April and discovered him. The empty syringe in his pocket and the cut soda can in the trash pointed to the cause, a heroin overdose.

“On both a personal and a professional level, we were all very shocked and of course worried about how this could happen in our spaces,” said Oak Park executive director David Seleb, who fired the security company responsible for clearing the library before closing.

The country’s heroin and painkiller problem has led to public overdoses in many places, but libraries are especially exposed. They’re free and open for whoever walks in, and lingering is welcome, no transaction or interaction required.

The American Library Association encourages librarians to get training on interacting with special populations, such as drug users and the homeless, but stresses the importance of partnering with groups such as police and social workers, said Julie Todaro, the association’s president.