Standard Active Last Updated: Dec 27, 2016
ASTM D7520-16

Standard Test Method for Determining the Opacity of a Plume in the Outdoor Ambient Atmosphere

Significance and Use

5.1 Air permits from regulatory agencies often require measurements of opacity from stationary air pollution point sources in the outdoor ambient environment. Opacity has been visually measured by certified smoke readers in accordance with USEPA (USEPA Method 9). DCOT is also a method to determine plume opacity in the outdoor ambient environment.

5.2 The concept of DCOT was based on previous method development using Digital Still Cameras and field testing of those methods.7,8 The purpose of this standard is to set a minimum level of performance for products that use DCOT to determine plume opacity in ambient environments.


1.1 This test method describes the procedures to determine the opacity of a plume, using digital imagery and associated hardware and software. The aforementioned plume is caused by particulate matter emitted from a stationary point source in the outdoor ambient environment.

1.2 The opacity of emissions is determined by the application of a Digital Camera Opacity Technique (DCOT) that consists of a Digital Still Camera, Analysis Software, and the Output Function’s content to obtain and interpret digital images to determine and report plume opacity.

1.3 This method is suitable to determine the opacity of plumes from zero (0) percent to one hundred (100) percent.

1.4 Conditions that shall be considered when using this method to obtain the digital image of the plume include the plume’s background, the existence of condensed water in the plume, orientation of the Digital Still Camera to the plume and the sun (see Section 8).

1.5 This standard describes the procedures to certify the DCOT, hardware, software, and method to determine the opacity of the plumes.

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

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Book of Standards Volume: 11.07
Developed by Subcommittee: D22.03
Pages: 22
DOI: 10.1520/D7520-16
ICS Code: 13.040.20