1.1 本试验方法涵盖了使用示踪气体稀释来确定由天气条件和机械通风引起的室外单区换气的技术。这些技术包括:( 1. )浓度衰减( 2. )恒定注入，以及( 3. )恒定浓度。 1.2 本试验方法仅限于任何单一示踪气体。相关数据分析假设可以用单个值表征区域内的示踪气体浓度。该区域应为建筑物、车辆、测试单元或任何符合要求的外壳。 1.3 使用该测试方法需要了解气体分析和仪器的原理。 正确使用此处给出的公式需要一致使用单位，尤其是时间单位。 1.4 确定分区外壳单个组件对换气的贡献超出了本试验方法的范围。 1.5 本试验方法的结果仅适用于测量期间盛行的天气和纬向运行条件。使用本试验结果预测其他条件下的换气量超出了本试验方法的范围。 1.6 本试验方法的文本参考了提供解释材料的注释和脚注。这些注释和脚注（不包括表和图中的注释和脚注）不应视为本试验方法的要求。 1.7 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。 1.8 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 换气的影响- 换气通常占建筑物供暖或空调负荷的很大一部分。它还影响建筑物内的水分和污染物平衡。通过建筑围护结构的含湿空气可能会导致冷凝并导致材料降解。所有建筑物都需要适当的通风水平；应该咨询ASHRAE 标准 62以确定建筑物的通风要求。 5.2 换气预测- 换气取决于漏气点的大小和分布、风和温度引起的压差、机械系统操作和乘客行为。 可以根据该信息计算换气量，但是，许多所需参数很难确定。示踪气体测试允许直接测量换气量。 5.3 测量的效用- 换气测量提供了有关通风和漏气的有用信息。在通风系统关闭的建筑物中进行测量，以确定自然漏风率是否高于规定值。通风系统运行时的测量用于确定换气是否满足或超过要求。 5.4 已知条件- 了解影响换气的因素使测量更有意义。 将建筑物对风和温度的响应联系起来需要在不同的气象条件下重复测试。将建筑响应与通风系统或居住者行为联系起来，需要控制这些因素的变化。 5.5 结果的适用性- 通过本试验方法中使用的技术获得的换气值适用于测量时盛行的特定条件。如果盛行风和温度条件发生变化，如果建筑物的操作不同，或者由于施工或劣化，测量之间的包络线发生变化，则同一建筑物的换气值将不同。 要确定漏气点，请遵循惯例 E1186 . 5.6 风扇增压- 相关技术（试验方法 E779 )使用风扇对建筑围护结构加压。通过测量信封上的相应气流和压差，将信封气密性表征为指定诱导压差下的漏气率或信封的等效泄漏面积。这些因素允许模拟由于风和温差引起的自然空气变化。然而，用试验方法无法直接测量自然换气 E779 . 试验方法 E779 允许对不同建筑物进行比较，隔离泄漏点，并评估改造措施。

1.1 This test method covers techniques using tracer gas dilution for determining a single zone's air change with the outdoors, as induced by weather conditions and by mechanical ventilation. These techniques are: ( 1 ) concentration decay, ( 2 ) constant injection, and ( 3 ) constant concentration. 1.2 This test method is restricted to any single tracer gas. The associated data analysis assumes that one can characterize the tracer gas concentration within the zone with a single value. The zone shall be a building, vehicle, test cell, or any conforming enclosure. 1.3 Use of this test method requires a knowledge of the principles of gas analysis and instrumentation. Correct use of the formulas presented here requires consistent use of units, especially those of time. 1.4 Determination of the contribution to air change by individual components of the zone enclosure is beyond the scope of this test method. 1.5 The results from this test method pertain only to those conditions of weather and zonal operation that prevailed during the measurement. The use of the results from this test to predict air change under other conditions is beyond the scope of this test method. 1.6 The text of this test method references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered requirements of this test method. 1.7 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. 1.8 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 Effects of Air Change— Air change often accounts for a significant portion of the heating or air-conditioning load of a building. It also affects the moisture and contaminant balances in the building. Moisture-laden air passing through the building envelope can permit condensation and cause material degradation. An appropriate level of ventilation is required in all buildings; one should consult ASHRAE Standard 62 to determine the ventilation requirements of a building. 5.2 Prediction of Air Change— Air change depends on the size and distribution of air leakage sites, pressure differences induced by wind and temperature, mechanical system operation, and occupant behavior. Air change may be calculated from this information, however, many of the needed parameters are difficult to determine. Tracer gas testing permits direct measurement of air change. 5.3 Utility of Measurement— Measurements of air change provide useful information about ventilation and air leakage. Measurements in buildings with the ventilation system closed are used to determine whether natural air leakage rates are higher than specified. Measurements with the ventilation system in operation are used to determine whether the air change meets or exceeds requirements. 5.4 Known Conditions— Knowledge of the factors that affect air change makes measurement more meaningful. Relating building response to wind and temperature requires repetition of the test under varying meteorological conditions. Relating building response to the ventilation system or to occupant behavior requires controlled variation of these factors. 5.5 Applicability of Results— The values for air change obtained by the techniques used in this test method apply to the specific conditions prevailing at the time of the measurement. Air change values for the same building will differ if the prevailing wind and temperature conditions have changed, if the operation of the building is different, or if the envelope changes between measurements because of construction or deterioration. To determine air leakage sites, follow Practices E1186 . 5.6 Fan Pressurization— A related technique (Test Method E779 ) uses a fan to pressurize the building envelope. Measurements of corresponding air flows and pressure differences across the envelope characterize envelope airtightness as either the air leakage rate under specified induced pressure differences or the equivalent leakage area of the envelope. These factors permit modeling natural air change due to wind and temperature differences. However, direct measurement of natural air change is not possible with Test Method E779 . Test Method E779 permits comparison of different buildings, isolation of leakage sites, and evaluation of retrofit measures.