5.1 Chamber testing is a globally-accepted method for measuring the emissions of VOCs from building materials and products. Chamber emission test data have a variety of uses including identification and labeling of products as low-VOC emitting for improved indoor air quality, manufacturing quality control, and development of new and improved products for reduced VOC emissions.
5.2 Currently, an inter-laboratory study (ILS) is the most frequently used method for assessing the bias of a laboratory’s VOC emission test results. An ILS typically relies on a VOC source with an uncharacterized emission rate. Consequently, a large number of participants (Practice E691 recommends 30, with a minimum requirement of six) are needed to produce the data required to calculate a laboratory’s performance relative to the central tendency and distribution of the results for all participants. Due to the participant size requirement and other logistical issues, an ILS involves significant planning and coordination to achieve useful results.
5.3 Inter-laboratory studies have often shown significant variations in measured VOC emission rates among participating laboratories for a given source. Variability in the emission rate from the source often is suspected to be a contributing factor, but it is difficult to be certain of the cause. Thus, better characterized sources are needed for evaluating the ability of laboratories to generate VOC emission test results with acceptable bias as discussed in 8.6.
5.4 Proficiency tests (PT) for VOC emission testing typically focus on a laboratory’s analytical capabilities. For example, an analytical PT relies on a certified standard prepared by an accredited vendor as a reference. A laboratory analyzes the PT sample without knowledge of its concentration value. Acceptance of the results is judged by the deviation from the known value. Use of reference materials can expand analytical PT schemes to also include the impacts of test sample handling, test specimen preparation, chamber operation, and chamber air sampling.
5.5 Laboratories accredited under ISO/IEC 17025 are required to derive uncertainty estimates for their test results. Typically, this is done by developing an uncertainty budget and estimating an expanded uncertainty (ISO/IEC Guide 98, Practice D7440). An uncertainty budget for a VOC emission test combines relevant sources of measurement uncertainty for all steps in the testing process from test specimen preparation through air sample analysis. A more efficient approach to determining the overall bias and precision for a VOC emission test is with repeated testing of a reference material (see ISO/IEC Guide 98, ISO Guide 33). This guide addresses the estimation of bias through comparison of the measured value to the reference material value. The precision is determined through repeated testing of multiple reference materials, ideally from the same production batch (see Practices D6299 and E691).
5.6 Other uses of an emissions reference material include verifying quality control emission measurements of manufactured product batches and providing traceability for third party certificatio......