Atmosphere (unit)
From Memory Alpha, the free Star Trek reference.
An atmosphere (atm) is a unit of measurement that describes the force exerted by the weight of air molecules in the atmosphere and is measured on Earth in pascals. 1 atm (standard atmosphere) is defined as 101,325 Pa.
The Federation typically measured the atmospheric pressure of planets they encountered by relating to "Earth-normal."
The atmospheric pressure of the habitats aboard the Nyrian biosphere vessel, encountered by USS Voyager in 2373, were kept at an Earth-normal atmosphere or 1 atm. (VOY: "Displaced")
