According to how the other half lives, where did the only fresh air for tenement rooms come from?

"From either the hallway or the stairs".

How the Other Half Lives: Studies among the Tenements of New York (1890) is the full name of the publication and it is a production which is termed as photojournalism by Jacob Riis, recording dingy living conditions in New York City ghettos in the eighteen-eighties. It filled in as a reason for future "muckraking" reporting by presenting the ghettos to New York City's upper and white collar classes.

this question does't support enough resioning to answer.

can you explain it better