<P> Standard conditions for temperature and pressure are standard sets of conditions for experimental measurements to be established to allow comparisons to be made between different sets of data . The most used standards are those of the International Union of Pure and Applied Chemistry (IUPAC) and the National Institute of Standards and Technology (NIST), although these are not universally accepted standards . Other organizations have established a variety of alternative definitions for their standard reference conditions . </P> <P> In chemistry, IUPAC has changed the definition of standard temperature and pressure (STP) in 1982: </P> <Ul> <Li> Until 1982, STP was defined as a temperature of 273.15 K (0 ° C, 32 ° F) and an absolute pressure of exactly 1 atm (1.01325 × 10 Pa). </Li> <Li> Since 1982, STP is defined as a temperature of 273.15 K (0 ° C, 32 ° F) and an absolute pressure of exactly 10 Pa (100 kPa, 1 bar). </Li> </Ul> <Li> Until 1982, STP was defined as a temperature of 273.15 K (0 ° C, 32 ° F) and an absolute pressure of exactly 1 atm (1.01325 × 10 Pa). </Li>

At stp the pressure of a gas is