The standard atmosphere (symbol: atm) is a unit of pressure defined as 101325 Pa (1.01325 bar). It is sometimes used as a reference or standard pressure.
nanopascals
The nanopascal is a multiple of the unit bit for Pressure. The prefix nano (symbol n) is defined in the International System of Units (SI) as a multiplier of 1.0 × 10-9 (1 billionth, short scale), and therefore 1 nanopascal = 1.0 × 10-9 pascals = 0.000000001 pascals. The nanopascal has the unit symbol nPa.