Quest is the joint airlock module used for US spacewalks on the International Space Station.
The Quest Joint Airlock was delivered and installed during Space Shuttle mission STS-104 in July 2001. It was built to support spacewalks using NASA's Extravehicular Mobility Unit suits, commonly called EMUs. Before Quest arrived, American astronauts generally needed a docked Space Shuttle to conduct an EVA using the shuttle's airlock.
Quest has two main sections: an equipment lock, where suits and tools are stored and prepared, and a crew lock, which is depressurised before astronauts exit into space. The module also carries oxygen and nitrogen supplies used to replenish the station's atmosphere and service spacesuits.
The name “joint” reflects the airlock's original ability to support both American EMU suits and Russian Orlan suits. Russian spacewalks can also use Russian-segment facilities such as Poisk. Tranquility is a station node, while Pirs was a former Russian docking and airlock compartment, so none of those is the US spacewalk airlock.