Atmosphere

An atmosphere was a collection of gases that surrounded a celestial body that possessed sufficient mass, and therefore sufficient gravity to hold it. Examples included many planets, moons, and large asteroids. Almost all species in the galaxy needed some form of atmosphere to breathe.

As humans were the predominant species within the Galactic Republic, later the Galactic Empire, a large number of planets within it possessed an atmosphere that supported human life, having a sufficient amount of oxygen.

Atmospheres habitable for oxygen-breathing species were referred to as "Type I atmospheres."

Moisture farms used vaporators to draw water from a planet's atmosphere.

The planet Quarzite had a strong atmospheric pressure that was capable of crushing starships and flattening beings.

Appearances
Technically, atmospheres appear in most Star Wars works. The following is a list of media in which atmospheres are specifically mentioned:
 * Star Wars: Episode III Revenge of the Sith
 * Tarkin
 * Lost Stars
 * The Rebellion Begins
 * Smuggler's Run: A Han Solo & Chewbacca Adventure
 * Battlefront: Twilight Company
 * Aftermath: Life Debt
 * Star Wars: The Force Awakens novel
 * Smuggler's Run: A Han Solo & Chewbacca Adventure
 * Battlefront: Twilight Company
 * Aftermath: Life Debt
 * Star Wars: The Force Awakens novel
 * Star Wars: The Force Awakens novel
 * Star Wars: The Force Awakens novel