scope:

This method covers the continuous recording of the mass concentration of particulate matter in the atmosphere in the size range of about 0.05 to 40 μm in diameter. Measurement is based on the light-scattering property of microscopic-size solid or liquid particles dispersed in gaseous medium.

The maximum range of concetration measured by means of this method is equivalent to 1 to 100,000 μg of particulate matter per cubic meter of air. Calibration within closer concentration limits will permit fullscale readings covering more narrow concentration ranges, thereby increasing the sensitivity to the test over the specific range being measured. The full range of concentration measurable by this method is equivalent to an estimated atmospheric visibility range from 900 miles to 50 ft. (1448 km to 15 m).

The mass concentration is strictly proportional to the scattered light intensity only when the particle size, shape, etc. remain constant. (See Note 10.) For information relative to meteorological and topographical factors affecting the application of this method, refer to ASTM Recommended Practice D 1357, Planning the Sampling of the Atmosphere. ²

_______

² Annual Book of ASTM Standards, Part 26.