ASTM D6561-20

5.1 HDI is mostly used in the preparation of paints. The use of isocyanates and their industrial needs have been in constant growth.

5.2 Diisocyanates and polyisocyanates are irritants to skin, eyes, and mucous membranes. They are recognized to cause respiratory allergic sensitization, asthmatic bronchitis, and acute respiratory intoxication 5.3 The American Conference of Governmental Industrial Hygienists (ACGIH) has adopted a threshold limit value–time weighted average (TLV-TWA) of 0.005 ppm (V) or 0.034 mg/m³ for monomeric HDI (7). The Occupational Safety & Health Administration of the U.S. Department of Labor (OSHA) has not listed a permissible exposure limit (PEL) for HDI (8).

5.4 In any case, there are not separate exposure standards for vapor and aerosol. Therefore, in comparing the results for isocyanate against a standard, results from the two fractions should be combined to give a single total value.

5.5 Due to its low LOD and low required volume (15 L), this test method is well suited for monitoring of respiratory and other problems related to diisocyanates and polyisocyanates. Its short sampling times are compatible with the duration of many industrial processes, and its low detection limit with the concentrations often found in the working area.

1.1 This test method covers the determination of aerosol hexamethylene diisocyanate (HDI) in air samples collected from workplace and ambient atmospheres. The method described in this test method collects separate fractions. One fraction will be dominated by vapor, and the other fraction will be dominated by aerosol. The results obtained from the analysis of the separate fractions do not necessarily represent the true partition of the measured HDI physical phases, and should only be considered a representation of the general trend in the physical phase partition within samples. The analyses of the two fractions are different, and are provided in separate, linked, standards to avoid confusion. This test method is principally used to determine short term exposure (15 min) of HDI in workplace environments for personal monitoring or in ambient air. The analysis of the vapor fraction is performed separately, as described in Test Method D6562.

1.2 Differential air sampling is performed with a segregating device. The aerosol fraction is collected on a polytetrafluoroethylene (PTFE) filter.

1.3 The analysis of the aerosol fraction is performed by using a high performance liquid chromatograph (HPLC) equipped with an ultraviolet (UV) detector. An ultra high performance liquid chromatograph (UPLC) can also be used, provided that its performance is equivalent to what is stated in this standard. The range of application of the test method has been validated from 0.052 to 1.04 μg of monomeric HDI/mL, which corresponds, based on a 15 L air sample, to concentrations from 0.004 to 0.070 mg/m³ of HDI. Those concentrations correspond to a range of aerosol phase concentrations from 0.5 ppb (V) to 10 ppb (V) and cover the established threshold limit valve (TLV) value of 5 ppb (V).

1.4 The quantification limit for the monomeric HDI is 0.041 μg per mL, which corresponds to 0.003 mg/m³ for a 15 L sampled air volume. This value is equivalent to ten times the standard deviation obtained from ten measurements carried out on a standard solution in contact with the PTFE filter whose concentration of 0.1 μg/mL is close to the expected detection limit.

1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.6 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. 1.7 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.