DSL - 220

Single pass opacity monitor for monitoring opacity and smoke emissions

The DSL-220 Opacity Monitor is an optical instrument designed to measure the visible opacity of exhaust gas in a duct, stack or flue.


Gas flow's measurement
In situ measurement directly in exhaust gas flow
Opacity's measurement
Measurement reading as % Opacity
Modulated green LED source
Modulated green LED source for long lifetime stability and immunity to ambient light
Rugged construction
Rugged 316 stainless steel construction
Interface options
Choice of interface options enabling easy integration
Free utility software
Free utility software for PC based set-up control and data logging
Optional Operator Interface
Optional Operator Interface with different mounting configurations

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The DSL-220 uses the single pass light transmission measurement technique, with Transmitter/Receiver arrangement. A light beam emitted from the Transmitter passes across the stack to a Receiver, which measures the intensity of the received light.

Increased particulate or smoke density in the stack gas attenuates the transmitted light and causes the intensity of the received light to fall. This reduction in intensity is measured and presented as % opacity. The higher the level of particulate or smoke present, the more light lost and therefore, the greater the opacity.

Optional accessories

  • Operator interface (OI)
  • 90-260 Vac model available
  • Mounting flange installation kit
  • Laser alignment tool to assist with installation
  • Air purge blower kit (110 Vac / 230 Vac / 415 Vac)
  • Compressed air purge kit
  • Reference filters for routine calibration check of the instrument


  • Low cost
  • Simple to install, commission and operate with an excellent reliability record
  • Rugged design with no moving parts so low maintenance
  • Latched head and lid design to enable ease of access for installation and maintenance


Discover Acoem’s case studies

Why do you need DSL-220 ?

Ideal for monitoring opacity and smoke levels in the exhaust gas of industrial combustion or air filtration processes.

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