ASTM D8460-22

SIGNIFICANCE AND USE 5.1 Vapor intrusion testing has been performed traditionally using multiple canister samples or thermal desorption tube samples. These discontinuous measurements have been shown to be snapshots and provide averages of exposure. In many cases a higher temporal resolution is desirable to identify peaks of emissions due to specific occupancy or environmental changes. For these cases, a continuous real-time monitoring solution is desirable. These continuous monitoring setups can be either short-term or be part of a long-term monitoring plan as described in ASTM guide “Standard Guide for the development of LongTerm Monitoring Plans for Vapor Mitigation Systems” (E2600). 5.2 The PTR-MS provides real-time measurement of multiple VOCs at ultra-trace levels, that is, in the µL/L (ppm) to less than pL/L (ppt) range. Its strengths lie with the ability to measure VOCs in real-time and continuously (that is, ~1 Hz or faster, using time-of-flight analyzers), and with limited sample pre-treatment, compared to a gas chromatograph (GC) system, which is commonly the method of choice to measure VOCs using a variety of detectors. In case of PTR-MS with quadrupole analyzers, the terms would be nearreal-time and semi-continuous. The high temporal resolution of the PTR-MS measurement in the range of second(s) is often desired when studying the atmospheric chemistry or source emissions that result in unpredictable, sudden, and short-term fluctuations. For a detailed description on the design and theory and practical aspects of operation for the different types of PTR-MS, please refer to Yuan et al. (2017)(1). 5.3 For ambient air measurements, such as vapor intrusion (VI) related emission testing, the PTR-MS can be used in three different modes of operation: (1) in scanning mode to identify sources and VI entry points within buildings; (2) in variation identification mode, as a continuous monitoring instrument with seconds to minutes of temporal resolution covering a large number of V... SCOPE 1.1 This test method describes a technique of quantifying the results from measuring various volatile organic compound contents using a chemical ionization mass spectrometer resulting in the production of positively charged target compound ions. Depending on the nature of production of so-called primary ions, the associated instruments having the capability to perform such analyses are either named Proton Transfer Reaction Mass Spectrometers (PTR-MS), Selected Ion Flow Tube Mass Spectrometers (SIFT-MS) or, in the most generic term, Mid-pressure chemical ionization mass spectrometers (MPCI-MS). Within this standard, the term PTR-MS is used to represent any of these instrumentations. 1.2 Either of the instrument types can be used with the two main mass analyzers on the market, that is, with either quadrupole (QMS) or time-of-flight (TOFMS) mass analyzer. This method relates only to the quantification portion of the analysis. Due to large differences in user interfaces and operating procedures for the instruments of the main instrument providers, the specifics on instrument operation are not described in this method. 1.3 Details on the theoretical aspects concerning ion production and chemical reactions are included in this standard as far as required to understand the quantification aspects and practical operation of the instrument in the field of vapor intrusion analyses. Specifics on the operation and/or calibration of the instrument need to be identified by using the user’s manual of the individual instrument vendor. A comprehensive discussion on the technique including individual mass-line interferences and in-depth comparison with alternate methods are given in multiple publications, such as Yuan et al. (2017) (1) and Dunne et al. (2018) (2)2. 1.4 Units—Values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. Reporting of test results in units othe...