1.1 本试验方法涵盖并适用于蒸汽压范围为35的汽油和汽油含氧混合物 kPa至100 千帕（5 psi至15 psi）（见 注释2 ). 本试验方法是对试验方法的修改 D323页 （里德方法），提供了两个程序来确定蒸汽压( 注1 )汽油和汽油含氧混合物。 注1: 由于外部大气压力被最初存在于气室中的大气压力抵消，因此该蒸汽压力为37.8的绝对压力 °C（100 °F），单位为千帕（磅力/平方英寸）。由于密闭空间中样品和空气的少量蒸发，该蒸汽压与样品的真实蒸汽压不同。 注2: 汽油或汽油含氧混合物的蒸汽压低于35 千帕（5 psi）或大于100 千帕（15 psi）可以用该测试方法确定，但精度和偏差（第 11 )不适用。对于蒸汽压大于100的材料 千帕（15 psi），使用0 kPa至200 kPa（0 psi至30 psi）试验方法附录中规定的仪表 D323页 . 1.2 当冷却到0时，一些汽油含氧混合物可能会出现雾状 °C至1 °C 9.4 ，应在结果报告中注明。模糊样本的精度和偏差声明尚未确定（见 附注7 ). 1.3 以国际单位制表示的数值应视为标准值。括号中给出的值仅供参考。 1.4 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 具体警告见 7.5 , 8.4.1 , 8.5.1 , 9.1 , A1.1 和 A1.1.3 . 1.5 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 蒸汽压是液体火花点火发动机燃料的一个重要物理特性。它指示燃料在不同操作条件下的性能。例如，蒸汽压是决定燃油是否会在高环境温度或高海拔下引起蒸汽锁定，或是否会在低环境温度下提供轻松启动的一个因素。 5.2 石油产品规范通常包括蒸汽压力限制，以确保产品具有适当的挥发性性能。 注3: 燃料的蒸汽压由各种政府机构调节。

1.1 This test method covers and is applicable to gasolines and gasoline-oxygenate blends with a vapor pressure range from 35 kPa to 100 kPa (5 psi to 15 psi) (see Note 2 ). This test method, a modification of Test Method D323 (Reid Method), provides two procedures to determine the vapor pressure ( Note 1 ) of gasoline and gasoline-oxygenate blends. Note 1: Because the external atmospheric pressure is counteracted by the atmospheric pressure initially present in the air chamber, this vapor pressure is an absolute pressure at 37.8 °C (100 °F) in kilopascals (pounds-force per square inch). This vapor pressure differs from the true vapor pressure of the sample due to some small vaporization of the sample and air in the confined space. Note 2: Vapor pressure of gasoline or gasoline-oxygenate blends below 35 kPa (5 psi) or greater than 100 kPa (15 psi) can be determined with this test method but the precision and bias (Section 11 ) do not apply. For materials with a vapor pressure greater than 100 kPa (15 psi), use a 0 kPa to 200 kPa (0 psi to 30 psi) gauge as specified in the annex of Test Method D323 . 1.2 Some gasoline-oxygenate blends may show a haze when cooled to 0 °C to 1 °C. If a haze is observed in 9.4 , it shall be indicated in the reporting of results. The precision and bias statements for hazy samples have not been determined (see Note 7 ). 1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific warnings are given in 7.5 , 8.4.1 , 8.5.1 , 9.1 , A1.1 , and A1.1.3 . 1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 Vapor pressure is an important physical property of liquid spark-ignition engine fuels. It provides an indication of how a fuel will perform under different operating conditions. For example, vapor pressure is a factor in determining whether a fuel will cause vapor lock at high ambient temperature or at high altitude, or will provide easy starting at low ambient temperature. 5.2 Petroleum product specifications generally include vapor pressure limits to ensure products of suitable volatility performance. Note 3: Vapor pressure of fuels is regulated by various government agencies.