1.1 This test method measures a function of the concentration of suspended particulate matter in the ambient atmospheres quickly and inexpensively. Hourly repetitive samples are taken automatically.

1.2 This test method does not provide results in mass/ volume units but in a method-defined unit, coefficient of haze per thousand linear feet (COH/1000 ft), which is directly related to the soiling effect of the sampled atmosphere when drawn through filter paper. Relations between COH/1000 ft and mass concentration measurements are dependent on the nature, size distribution, shape, and refractive index of the particulate matter. When these factors are constant at one site, a useful relationship between COH/1000 and mass concentration values can often be developed.

1.3 This test method can accommodate low and high concentrations of suspended particulate matter by alteration of the sample volume by means of flow rate or sampling time changes.

1.4 This test method is not applicable when fog or mist are present in the sampled atmosphere because wet filter paper has a flow resistance so high that the sample pump will not be able to draw sample air through the paper.

1.5 The transfer of the sample from the atmosphere to the instrument will precipitate some of the particulate matter on the walls of the tubing used. Guidelines to minimize this effect are included below, but this test method is limited to situations in which a short sampling line, that is, less than 15 ft, can be provided.

1.6 The accuracy, reproducibility, and usefulness of this and other test methods for measurements of suspended particulate matter in the ambient atmosphere are limited severely by the absence of primary calibration standards ("standard dirty air"), and by the characterization of a complex and variable material, suspended particulate matter, by a single property (soiling effect, mass per volume, etc.). These limitations should be borne in mind constantly when a test method is selected and results from it are evaluated.

1.7 This test method is not designed to be used for industrial hygiene monitoring in the absence of other more specific monitoring test methods.

1.8 A complete SI companion to Test Method D1704 has been developed, D1704M; therefore, no SI equivalents are given in this test method. See Annex A1 for conversion of data from one test method to the other.

1.9 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 and health practices and determine the applicability of regulatory limitations prior to use.