1.1 本规程涵盖了一种用于监测暴露在产生水分沉积的循环大气条件下的表面上的湿润时间（TOW）的技术。 1.2 本规程也适用于检测和监测墙壁或屋顶组件内以及试验装置中的冷凝。 1.3 如果测量TOW以与其他位置进行比较，尤其是如果将该数据与其他特定位置的仪器技术结合使用，则可以显著增强暴露位置校准或表征。 1.4 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.5 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。 1.6 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====== 3.1 本规程提供了一种测量安装在感兴趣位置表面上的传感元件的湿润持续时间的方法。经验表明，传感元件对导致潮湿的因素的反应方式与其安装表面相同。 3.2 表面水分在金属腐蚀和非金属变质中起着关键作用。表面上的水分沉积可能是由大气或气候现象引起的，例如雨或雪的直接沉淀、冷凝、腐蚀产物的潮解（或至少是吸湿性）或表面上的盐沉积等。 对导致水分沉积的大气或气候因素的测量不一定能准确指示拖航。例如，物体的表面温度可能高于或低于环境温度和露点温度。因此，在没有环境气象指示的情况下，表面将发生冷凝循环。 3.3 如中所述，结构设计因素和方向可能会导致温差以及由此对拖车的影响 4.2 . 因此，一些表面可能会被雨雪遮挡；可以促进或阻止特定区域的排水，等等。 因此，根据质量、方向、气流模式等，可以预期结构的各种组件的性能不同。了解大型结构物上不同点处的拖缆有助于解释腐蚀或其他测试结果。 3.4 为了改进从宏观地理基础上分离的测试位置获得的数据的比较，建议在盛行风方向上以高于水平30°的角度均匀暴露传感器元件。应记录传感器高于地面的高度。 3.5 虽然该方法没有建立TOW与环境相对湿度（RH）水平之间的关系，但已进行了长期研究，以表明在标准条件下暴露的面板每年经历的TOW相当于RH高于给定阈值的累积时间。 2. 该时间值随位置和其他因素而变化。已经为一个位置的标准面板的顶部和底部表面绘制了概率曲线，该曲线显示了表面湿润的可能时间，作为相对湿度处于特定水平的累积时间的百分比。 3. 如果需要，应该可以建立类似的关系来处理其他暴露条件。

1.1 This practice covers a technique for monitoring time-of-wetness (TOW) on surfaces exposed to cyclic atmospheric conditions which produce depositions of moisture. 1.2 The practice is also applicable for detecting and monitoring condensation within a wall or roof assembly and in test apparatus. 1.3 Exposure site calibration or characterization can be significantly enhanced if TOW is measured for comparison with other sites, particularly if this data is used in conjunction with other site-specific instrumentation techniques. 1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.5 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. 1.6 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 ====== 3.1 This practice provides a methodology for measuring the duration of wetness on a sensing element mounted on a surface in a location of interest. Experience has shown that the sensing element reacts to factors that cause wetness in the same manner as the surface on which it is mounted. 3.2 Surface moisture plays a critical role in the corrosion of metals and the deterioration of nonmetallics. The deposition of moisture on a surface can be caused by atmospheric or climatic phenomena such as direct precipitation of rain or snow, condensation, the deliquescence (or at least the hygroscopic nature) of corrosion products or salt deposits on the surface, and others. A measure of atmospheric or climatic factors responsible for moisture deposition does not necessarily give an accurate indication of the TOW. For example, the surface temperature of an object may be above or below both the ambient and the dew point temperatures. As a result condensation will occur without an ambient meteorological indication that a surface has been subjected to a condensation cycle. 3.3 Structural design factors and orientation can be responsible for temperature differences and the consequent effect on TOW as discussed in 4.2 . As a result, some surfaces may be shielded from rain or snow fall; drainage may be facilitated or prevented from given areas, and so forth. Therefore various components of a structure can be expected to perform differently depending on mass, orientation, air flow patterns, and so forth. A knowledge of TOW at different points on large structures can be useful in the interpretation of corrosion or other testing results. 3.4 In order to improve comparison of data obtained from test locations separated on a macrogeographical basis, a uniform orientation of sensor elements boldly exposed in the direction of the prevailing wind, at an angle of 30° above the horizontal is recommended. Elevation of the sensor above ground level should be recorded. 3.5 Although this method does not develop relationships between TOW and levels of ambient relative humidity (RH), long term studies have been carried out to show that the TOW experienced annually by panels exposed under standard conditions is equivalent to the cumulative time the RH is above a given threshold value. 2 This time value varies with location and with other factors. Probability curves have been developed for top and bottom surfaces of a standard panel at one location which show the probable times that a surface will be wet as a percentage of the cumulative time the relative humidity is at specific levels. 3 If needed, it should be possible to develop similar relationships to deal with other exposure conditions.