Abbreviation for standard temperature (273.15 K or 0°C) and pressure (10E5 Pa); usually employed in reporting gas volumes. Note that flow meters calibrated in standard gas volumes per unit time often refer to volumes at 25°C, not 0°C.
See also: standard conditions for gases
PAC, 1990, 62, 2167. 'Glossary of atmospheric chemistry terms (Recommendations 1990)' on page 2217 (https://doi.org/10.1351/pac199062112167)