In chemistry, IUPAC changed its definition of standard temperature and pressure in 1982: 
* Until 1982, STP was defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 1 atm (101.325 kPa). 
* Since 1982, STP has been defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 10 Pa (100 kPa, 1 bar).
NIST uses a temperature of 20 °C (293.15 K, 68 °F) and an absolute pressure of 1 atm (14.696 psi, 101.325 kPa). This standard is also called normal temperature and pressure (abbreviated as NTP). However, a common temperature and pressure in use by NIST for thermodynamic experiments is 298.15 K (25°C, 77°F) and 1 bar (14.5038 psi, 100 kPa).  NIST also uses "15 °C (59 °F)"  for the temperature compensation of refined petroleum products, despite noting that these two values are not exactly consistent with each other.
The ISO 13443 standard reference conditions for natural gas and similar fluids are  and 101.325 kPa;
by contrast, the American Petroleum Institute adopts .