1.1 目的- 本规程涵盖了从渗流区被动收集土壤气体样本的标准化技术，并将与指南一起使用 D5314 . 1.2 目标- 指导本实践发展的目标是:（1）综合并编写进行被动土壤气体采样的良好商业和惯例，（2）确保收集和分析被动土壤气体样本的过程实用合理，（3）为被动土壤气体采样提供标准指南，以支持源识别、空间变异性/范围确定、现场评估、现场监测和蒸汽侵入调查。 1.3 本规程不涉及任何联邦、州或地方法规或指南或两者关于土壤气体采样的要求。 提醒用户，联邦、州和地方指南可能会提出与本实践不同的具体要求。 1.4 单位- 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 本实践提供了一组用于执行一个或多个特定操作的说明。本文件不能取代教育或经验，应与专业判断一起使用。并非本惯例的所有方面都适用于所有情况。 本ASTM标准不代表或取代必须根据其判断给定专业服务的充分性的谨慎标准，也不应在不考虑项目的许多独特方面的情况下应用本文件。标题中的“标准”一词仅表示该文件已通过ASTM共识程序获得批准。 1.7 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 被动土壤气体采样器是一种微创、易于使用的现场技术，用于识别渗流区的挥发性有机化合物和挥发性有机化合物。 与主动土壤气体和其他现场筛选技术类似，被动采样器的简单性和低成本使其能够大量应用，便于对整个现场的污染进行详细测绘，以识别污染源区域和释放位置，重点关注后续土壤和地下水采样位置，重点关注补救计划，识别蒸汽侵入途径，跟踪地下水羽流，并监测修复进度。被动土壤气体采样产生的数据是半定量的，取决于采样人员控制内外的许多因素。关键变量在以下章节中确定并简要讨论。 注1: 关于这些因素或变量的其他非强制性信息包含在第节中引用的适用标准中 2. ，以及随附的脚注和参考书目。 5.2 应用程序- 本规程中描述的技术适用于在各种地质环境下使用吸附剂取样器对土壤气体进行采样，以进行后续VOCs和SVOCs分析。该技术也可能被证明对VOC和SVOC以外的物种有用，例如元素汞，具有专门的吸附剂介质和分析。 5.2.1 源识别和空间变异性评估- 被动土壤气体采样是一种有效的方法，可以识别渗流区的污染源区域并确定污染程度。通过在数据间隙较小的网格中收集样本，该方法可以增加数据密度，因此可以高分辨率地描述整个调查区域的污染性质和程度。 通过从一个位置到另一个位置对结果进行定性或定量比较，可以确定地下污染物的相对分布和空间变异性，从而改进概念现场模型。报告未检测到的现场区域可以从进一步调查中删除，而后续的采样和补救可以集中在PSG调查确定的受影响区域。 5.2.2 监测- 被动土壤气体采样器用于监测现场条件的变化（例如，现场的新释放，现场或场外来源的地下水中污染物浓度的增加，以及补救系统性能的有效性），随着时间的推移，固定位置的土壤气体结果的变化反映了这一变化。收集初始数据集以建立基线，并收集后续数据集以进行比较。 采样和分析程序应尽可能保持恒定，以便土壤气体结果的显著变化可归因于现场地下污染物水平的变化，从而保证进一步调查以确定原因。 5.2.3 蒸汽侵入评估- 被动土壤气体采样可用于识别蒸汽迁移和侵入途径（见实践 E2600 )数据提供了一系列证据，证明土壤蒸汽中是否存在化合物，与潜在受体相关的性质和程度，以及蒸汽途径是否完整。吸附剂取样器可放置在楼板下方或建筑物附近，以收集针对挥发性有机物和挥发性有机物的时间积分样本，其浓度通常低于活性土壤气体采样方法的浓度。 5.3 限制- 被动土壤气体数据以每个样本位置确定的单个化合物或化合物组的质量报告，报告单位通常为纳克（ng）或微克（μg），而不是浓度（见 6.8 ). 理想情况下，使用该方法产生的数据将代表时间加权土壤气体浓度，存在于PSG采样器附近，并在暴露期间吸附在采样器上；然而，取样器设计的不均匀性、样品采集期间的饥饿效应或导致吸附剂表面积饱和的吸附剂量不足，或其组合，将影响吸附质量和土壤气体浓度之间的关系。这些数据代表任何较大区域或不同时间的程度取决于许多现场- 具体因素。通常，仅从被动土壤气体采样程序获得的信息不足以支持土壤气体浓度的定量测定。 5.4 采样器设计- 如果技术设计中包括适当的质量控制，包括采样器结构的均匀性，则被动土壤气体是一种有效的调查/监测工具。至少，应采取控制措施，以确保（1）使用具有疏水性的适当吸附剂来针对相关化合物（见实践） D6196 )，（2）用于容纳吸附剂的材料具有化学惰性、非反应性或腐蚀性，不会产生废气化合物或充当竞争吸附剂（见指南） D5314 第6.5.3）段）和（3）将吸收剂放置在适当的容器中，以保护吸收剂，允许土壤气体扩散到吸收剂，并便于将取样器安装到所需的采样深度。 5.4.1 取样器调节- 在将PSG取样器送至现场进行部署之前，应对其进行调节，以清除吸着剂和取样器材料上或其中存在的任何潜在污染，或在取样器施工或使用前储存期间遇到的任何潜在污染。调节过程应不损害吸附剂的吸附能力。调节后，将取样器盖上盖子/重新密封，并将其存储在一个容器中，该容器在现场采集样品前后（包括运输期间）提供足够的保护，以防止周围污染源。应对每批经过处理的取样器的制备空白进行分析，以验证吸附剂经过有效处理，并且不会保留超过报告限值的目标化合物的可测量质量。此外，当往返现场的所有货物中包含行程空白时，报告非- 对于目标化合物的检测，这些QC样品提供了额外的证据，证明采样器经过调节后没有可测量的目标化合物质量，并且现场样品的测量结果来自现场本身。 5.5 取样器暴露期- 源识别、空间变异性评估和蒸汽侵入评估的PSG暴露期指南应考虑项目目标、目标化合物、所需检测限值或预期土壤气体浓度或两者、被动采样器的设计、基质异质性、土壤类型（总孔隙度）、土壤含水量（充水孔隙度），以及预期污染物的深度。具有粗粒干燥土壤、高浓度、浅层地下水或土壤污染或两者兼有以及挥发性化合物的场地通常需要较短的暴露时间。 具有细粒、粘土或潮湿土壤或两者兼有、深层污染源、低浓度或SVOCs或其组合的场地通常需要更长的暴露时间。暴露期通常从几天到几周不等，但当土壤蒸汽中预期有高浓度的目标化合物时，暴露期可能短至一小时。 5.6 取样器间距- 网格设计可以包括规则间隔的采样器位置，随机或不规则间隔，以及样带或不同的空间间隔（见指南 D6311 ). 偏置间距，其中在已知或可疑目标的区域（即源区域）使用较小的样本间距，在不认为受到影响的区域使用较大的间距。对于大面积调查，可以使用分阶段或分阶段采样程序。研究从大间距规则网格设计开始。 审查初始土壤气体结果，并在观察到目标化合物的位置进行后续采样。随后的调查设计由更紧密的样本组成，以更详细地解决感兴趣的特征。土壤气体采样的多个阶段可以结合在一起，以提供土壤气体结果的一个全面图像。分阶段或分阶段调查需要多次部署，从而增加了总体调查的成本。然而，现场土壤气体中具有不可检测值的区域可从进一步调查中移除。 5.6.1 没有规定或设置适用于所有现场的采样器间距，因为样本间距和调查设计基于项目目标，每个现场都是唯一的。采样器间距的一般建议范围为3至30 m，7。 缺乏现场知识时，间距为5-15米。建议在最初具有更大样本间距的区域进行填充采样。 5.6.2 现场具体信息（调查区域大小、地下水深度、土壤类型和含水量、调查目的、， 等 )在确定使用的网格间距时，应与这些指南一起考虑。网格单元大小的选择（网格模式中部署的采样器间距的直接函数）在很大程度上取决于项目置信水平和预算要求之间的关系。预算有限的研究人员倾向于使用过大的网格单元间距。这种“欠采样”行为通常会导致不充分、过度解释的数据，并得出不支持的结论。应注意避免该问题（指南 D5314 ). 在设计有效的土壤气体调查以开发合理的概念现场模型时，通过预算平衡的调查目标应确定样本间距。 5.7 采样深度- 在确定部署深度时，应考虑项目目标。在可能的情况下，最好在相同深度部署采样器，以确保数据一致性。PSG取样器通常安装在15 cm至1.0 m BLS的深度；然而，在适当的情况下，可以将孔推进到更大的深度，取样器也可以悬挂在表面通量室下方或永久蒸汽口中。 5.8 土壤类型- 一般来说，砂质土壤往往更具多孔性和渗透性，因此需要更短的暴露时间。相反，粘土含量高的土壤往往多孔性和渗透性较差，通常具有较低的通量（见实践） D2487 ). 由于充满空气的孔隙的数量和互连性不同，土壤类型的蒸汽渗透性也不同。孔隙中填充的空气越多、相互连接越多，污染物通过土壤流向采样器的潜在通量就越大。导致低偏差的饥饿效应更可能发生在低渗透性土壤中，其中通过土壤基质的通量有限。 5.9 土壤水分的影响- 由于从地下来源到被动取样器的蒸汽扩散依赖于土柱内相互连接且充满空气的孔隙，因此土壤水分可能对污染物的通量产生重大影响，从而对采样装置可吸附的污染物质量产生重大影响。使用疏水性吸附剂可将对采样器灵敏度的影响降至最低，但不会改变土壤湿度对污染物土壤气体浓度的影响。 因此，土壤水分高的区域可能比土壤水分低的区域具有显著更低的土壤气体结果，即使这两个区域的地下浓度相似。因此，了解土壤水分条件有助于解释土壤气体结果。这些知识对于比较在现场进行的后续调查的结果也很有用。 5.10 目标化合物的作用- 一般来说，目标化合物的分子量越大，土壤气体中的蒸汽压和由此产生的浓度越低，因此，包气带中PSG取样器所需的暴露时间越长。 5.11 密封（堵塞）孔顶部- 一旦将PSG取样器插入地面，孔的顶部就会被一种可以有效密封孔的材料堵住，例如铝箔或软木，然后可以用土壤覆盖。 对于混凝土或沥青铺面，可选择在塞子上方使用约5 mm厚的砂浆或速凝混凝土修补片，以在取样器位于地面时保持表面的完整性。用于堵塞孔的材料不应产生令人担忧的化合物，密封件应齐平安装，以确保采样器免受伤害，防止环境空气或地表水进入，并且在暴露期间不会中断正在进行的现场活动。 5.12 安装/回收采样器时环境空气的影响- PSG取样器到达现场时应密封，以保护吸附剂在运输过程中免受环境空气中污染物的影响。就在安装到孔中之前，然后在取回过程中，将取样器暴露在环境空气中一小段时间。暴露在环境空气中的典型时间小于15秒。 在某些情况下，可能需要使用PSG采样器收集现场空白，以评估环境空气中的化合物是否可能对结果产生偏差。为了执行该质量控制检查，打开一个相同的PSG采样器，并将其暴露在环境空气中大约相同的时间，以安装PSG采样器，然后在指定位置取回PSG采样器。现场空白在所有其他时间均密封，并与现场样品一起运输至实验室。在现场活动期间，应注意尽量减少吸附剂暴露在环境空气中。安装/取回取样器时，明显的污染源（例如，燃气发电机或车辆排气）不应靠近取样器。 注2: 本标准产生的结果的质量取决于执行该标准的人员的能力以及所用设备和设施的适用性。 符合实践标准的机构 D3740 通常认为能够胜任和客观的测试/采样/检查等。本标准的用户应注意遵守惯例 D3740 本身并不能保证可靠的结果。可靠的结果取决于许多因素；实践 D3740 提供了一种评估其中一些因素的方法。

1.1 Purpose— This practice covers standardized techniques for passively collecting soil gas samples from the vadose zone and is to be used in conjunction with Guide D5314 . 1.2 Objectives— Objectives guiding the development of this practice are: (1) to synthesize and put in writing good commercial and customary practice for conducting passive soil gas sampling, (2) to ensure that the process for collecting and analyzing passive soil gas samples is practical and reasonable, and (3) to provide standard guidance for passive soil gas sampling performed in support of source identification, spatial variability/extent determinations, site assessment, site monitoring, and vapor intrusion investigations. 1.3 This practice does not address requirements of any federal, state, or local regulations or guidance or both with respect to soil gas sampling. Users are cautioned that federal, state, and local guidance may impose specific requirements that differ from those of this practice. 1.4 Units— 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 practice offers a set of instructions for performing one or more specific operations. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this practice may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. The word “Standard” in the title means only that the document has been approved through the ASTM consensus process. 1.7 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 Passive soil gas samplers are a minimally invasive, easy-to-use technique in the field for identifying VOCs and SVOCs in the vadose zone. Similar to active soil gas and other field screening techniques, the simplicity and low cost of passive samplers enables them to be applied in large numbers, facilitating detailed mapping of contamination across a site, for the purpose of identifying source areas and release locations, focusing subsequent soil and groundwater sampling locations, focusing remediation plans, identifying vapor intrusion pathways, tracking groundwater plumes, and monitoring remediation progress. Data generated from passive soil gas sampling are semi-quantitative and are dependent on numerous factors both within and outside the control of the sampling personnel. Key variables are identified and briefly discussed in the following sections. Note 1: Additional non-mandatory information on these factors or variables are covered in the applicable standards referenced in Section 2 , and the footnotes and Bibliography presented herewith. 5.2 Application— The techniques described in this practice are suitable for sampling soil gas with sorbent samplers in a wide variety of geological settings for subsequent analysis for VOCs and SVOCs. The techniques also may prove useful for species other than VOCs and SVOCs, such as elemental mercury, with specialized sorbent media and analysis. 5.2.1 Source Identification and Spatial Variability Assessment— Passive soil gas sampling can be an effective method to identify contaminant source areas in the vadose zone and delineate the extent of contamination. By collecting samples in a grid with fewer data gaps, the method allows for an increase in data density and, therefore, provides a high-resolution depiction of the nature and extent of contamination across the survey area. By comparing the results, as qualitative or quantitative, from one location to another, the relative distribution and spatial variability of the contaminants in the subsurface can be determined, thereby improving the conceptual site model. Areas of the site reporting non-detects can be removed from further investigation, while subsequent sampling and remediation can be focused in areas determined from the PSG survey to be impacted. 5.2.2 Monitoring— Passive soil gas samplers are used to monitor changes in site conditions (for example, new releases on-site, an increase in contaminant concentrations in groundwater from onsite or off-site sources, and effectiveness of remedial system performance) as reflected by the changes in soil gas results at fixed locations over time. An initial set of data is collected to establish a baseline and subsequent data sets are collected for comparison. The sampling and analytical procedures should remain as near to constant as possible so significant changes in soil gas results can be attributed to those changes in subsurface contaminant levels at the site that will then warrant further investigation to identify the cause. 5.2.3 Vapor Intrusion Evaluation— Passive soil gas sampling can be used to identify vapor migration and intrusion pathways (see Practice E2600 ), with the data providing a line of evidence on the presence or absence of the compounds in soil vapor, the nature and extent in relation to potential receptors, and whether a vapor pathway is complete. Sorbent samplers can be placed beneath the slab or in close proximity to buildings to collect time-integrated samples targeting VOCs and SVOCs at concentrations often lower than can be achieved with active soil gas sampling methods. 5.3 Limitations— Passive soil gas data are reported in mass of individual compounds or compound groups identified per sample location, with the reporting units generally in nanograms (ng) or micrograms (μg) per sampler and not a concentration (see 6.8 ). Ideally, the data produced using this method will be representative of time-weighted soil gas concentrations, present in the vicinity of the PSG sampler and sorbed on the sampler during the exposure period; however, non-uniformity of sampler design, starvation effects during sample collection, or an insufficient amount of sorbent that results in saturation of the sorbent surface area, or combinations thereof, will affect the relationship between sorbed mass and soil gas concentrations present. The degree to which these data are representative of any larger areas or different times depends on numerous site-specific factors. In general, information obtained from a passive soil gas sampling program alone is not sufficient to support a quantitative determination of soil gas concentrations. 5.4 Sampler Design— Passive soil gas is an effective investigatory/monitoring tool if the appropriate quality controls are included in the technology design, which includes uniformity in the construction of the sampler. At a minimum, controls should be in place to ensure that (1) the appropriate sorbents with hydrophobic properties are used to target the compounds of concern (see Practice D6196 ), (2) materials used to house the sorbents are chemically-inert, non-reactive or corrosive, and will not off-gas compounds or act as competing sorbents (see Guide D5314 , paragraph 6.5.3), and (3) the sorbents are housed in suitable containers that protect the sorbents, allow diffusion of the soil gas to the sorbents, and facilitate installation of the sampler to the desired sampling depth. 5.4.1 Sampler Conditioning— Before being sent to the field for deployment, the PSG sampler should be conditioned to remove any potential contamination present on or in the sorbent and sampler materials or both encountered during sampler construction or storage prior to use. The conditioning process should be one that does not damage the sorptive capability of the sorbent. Following conditioning, the sampler is then capped/resealed and stored in a container that provides adequate protection against ambient sources of contamination before and after sample collection in the field, including during transport. Preparation blanks from each batch of conditioned samplers should be analyzed to verify that the sorbents were effectively conditioned and do not retain measurable masses of target compounds above reporting limits. Furthermore, when trip blanks, which are included with all shipments to and from the field, report non-detects for the targeted compounds, these QC samples provide additional evidence that the samplers were conditioned to have no measurable mass of target compounds and that the measurements on field samples originate from the site itself. 5.5 Sampler Exposure Periods— Guidelines for PSG exposure periods for source identification, spatial variability assessment, and vapor intrusion evaluation should consider the project objectives, target compounds, required detection limits or anticipated soil gas concentrations or both, design of the passive sampler, matrix heterogeneity, soil types (total porosity), soil moisture level (water filled porosity), and depth to expected contaminants. Sites having coarse-grained dry soils, high concentrations, shallow groundwater or soil contamination or both, and volatile compounds typically require shorter exposure periods. Sites with finegrained, clays or moist soils or both, deep contaminant sources, low concentrations, or SVOCs, or combinations thereof, typically require longer exposure periods. Exposure periods typically range from days to weeks but can be as brief as one hour when high concentrations of target compounds are expected in the soil vapor. 5.6 Sampler Spacing— Grid designs can consist of regularly spaced sampler locations, random or irregular spaced, and as transects or varying spatial intervals (see Guide D6311 ). Biased spacing in which smaller sample spacing is used in areas with known or suspected targets (that is, source areas) and large spacing in areas not believed to be impacted are also used. For large area investigations, a staged or phased sampling program can be used. The investigation begins with a widely spaced regular grid design. The initial soil gas results are reviewed and subsequent sampling is conducted at locations where the target compounds were observed. The subsequent survey design consists of more closely spaced samples to resolve the feature of interest in greater detail. Multiple phases of soil gas sampling can be combined to provide one comprehensive image of the soil gas results. Staged or phased investigations require multiple deployments adding costs to the overall investigations. However, areas of the site that have nondetectable values in the soil gas may be removed from further investigation. 5.6.1 There is no prescribed or set sampler spacing appropriate for all sites, as sample spacing and survey design are based on project objectives and each site is unique. General recommendations for sampler spacing range from 3 to 30 m, with 7.5- to 15-m spacing when site knowledge is lacking. Infill sampling is recommended in areas having wider sample spacing initially. 5.6.2 Site-specific information (investigation area size, groundwater depth, soil type and moisture content, purpose of the investigation, etc. ) should be considered along with these guidelines in determining the grid spacing used. The selection of grid cell size (a direct function of the sampler spacing deployed in a grid pattern) is strongly dependent upon the relationship between both project confidence level and budget requirements. The tendency exists for investigators with constrained budgets to use overly large grid cell spacing. This action of “undersampling” normally results in inadequate, over-interpreted data with unsupported conclusions. Care shall be taken to avoid this problem (Guide D5314 ). In designing an effective soil gas survey to develop a rational conceptual site model, the survey objective balanced by budget should determine the sample spacing. 5.7 Sampling Depth— Consideration of project objectives should be taken into account when determining deployment depth. It is ideal, when possible, to deploy samplers at the same depth to ensure data consistency. PSG samplers are generally installed from a depth of 15-cm to 1.0-m BLS; however, holes may be advanced to greater depths when appropriate, and samplers can also be suspended beneath surface flux chambers or in permanent vapor ports. 5.8 Soil Types— In general, sandy soils tend to be more porous and permeable and, thus, require shorter exposure times. Conversely, soils with high clay contents tend to be less porous and permeable and typically have lower flux rates (see Practice D2487 ). Soil types vary in vapor permeability due to the differences in the number and interconnectivity of air-filled pores. The more air-filled, interconnected the pores are, the greater the potential flux of contaminants through the soil to the sampler. Starvation effects resulting in low bias are more likely to occur in low permeability soils where the flux through the soil matrix is limited. 5.9 Effects of Soil Moisture— Because diffusion of vapors from subsurface sources to passive samplers relies on interconnected and air-filled pores within the soil column, soil moisture can have a significant effect on the flux of contaminants and, therefore, the mass of the contaminant available for adsorption by the sampling device. The use of hydrophobic sorbents minimizes the effect on sampler sensitivity, but does not change the impact of soil moisture on contaminant soil gas concentrations. As a result, areas of high soil moisture may have significantly lower soil gas results than areas of low soil moisture, even though subsurface concentrations are similar in both areas. Therefore, some knowledge of the soil moisture conditions can help in interpreting soil gas results. This knowledge is also useful for comparing results from subsequent surveys performed at a site. 5.10 Effects of Target Compounds— In general, the larger the molecular weight of the compounds being targeted, the lower the vapor pressure and resulting concentrations in the soil gas, and therefore, the longer the required exposure time of the PSG samplers in the vadose zone. 5.11 Sealing (Plugging) the Top of the Hole— Once the PSG sampler is inserted in the ground, the top of the hole is plugged with a material that will effectively seal the hole, such as aluminum foil or cork, which can then be covered with soil. For concrete or asphalt surfacing, an approximately 5-mm-thick mortar or quick-setting concrete patch above the plug can be used as an option to maintain the integrity of the surface while the sampler is in the ground. The materials used to plug the hole should not contribute compounds of concern and the seal should be flush mounted to keep the sampler safe from harm, prevent ingress of ambient air or surface water, and not interrupt ongoing site activities during the exposure period. 5.12 Effects of Ambient Air While Installing/Retrieving Samplers— PSG samplers arrive at the site sealed to protect the sorbents from contaminants in ambient air during transport. Just prior to installation into the hole, and then again during retrieval, the sampler is exposed to ambient air for a brief period of time. The typical time of exposure to the ambient air is less than 15 s. In some instances, it may be necessary to collect a field blank using a PSG sampler to evaluate whether compounds in the ambient air potentially biased the results. To perform this quality control check, an identical PSG sampler is opened and exposed to the ambient air for approximately the same amount of time required to install and then later retrieve a PSG sampler at a designated location. The field blank is sealed at all other times and is transported to the laboratory along with the field samples. Care should be taken to minimize the sorbent exposure to ambient air during field activities. Obvious sources of contamination (for example, gas-powered electrical generators or vehicle exhaust) should not be in close proximity when installing/retrieving a sampler. Note 2: The quality of the result produced by this standard is dependent on the competence of the personnel performing it and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection/and so forth. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.