Double pass opacity monitor for monitoring opacity and particle emissions

The DSL-460 Opacity Monitor is an optical instrument designed to measure the visual opacity and/or concentration of dust or particulate matter in an exhaust gas passing through a duct, stack or flue.


Gas flow's measurement
In situ measurement directly in exhaust gas flow
Opacity and particulate measurement
Measurement reading as % opacity and/or particulate as mg/m³
Modulated green LED source
Modulated green LED source for long lifetime stability and immunity to ambient light
Rugged construction
Rugged 316 stainless steel construction
Visual alignment
Integrated visual alignment aid to simplify installation
In-situ zero and calibration check facility
‘Intelligent’ sensor
‘Intelligent’ sensor with optional DSCU operator interface with dual parameter display
Interface options
Choice of interface options enabling easy integration

See our technology in action.

Schedule a free demo to get a first-hand look at how our solutions support your business.

DSL-460 MkII

The DSL-460 uses the double pass light transmission measurement technique, with a folded beam Transceiver/Reflector arrangement. A light beam emitted from the Transceiver (TRX) passes across the duct, stack or flue to a Reflector, which then returns the light to the Transceiver where the intensity of the received light is measured.

Increased particulate density in the stack gas attenuates the transmitted light and causes the intensity of the received light to fall. This reduction in intensity can be presented as % opacity or when calibrated against standard reference measurements, this reduction in intensity can be used to calculate the particulate concentration and present a reading in mg/m³.

Optional accessories

  • DSCU operator interface with dual parameter display
  • 90-260 Vac model available
  • Mounting flange installation kit
  • Air purge blower kit (110 Vac / 230 Vac / 415 Vac)
  • Compressed air purge kit
  • Reference filters for routine calibration check of the instrument
  • External weather covers for TRX and Reflector heads


  • Plug and socket connectors for ease of installation
  • Simpler installation than single pass opacity monitors with better accuracy over shorter path lengths
  • Rugged design with no moving parts so low maintenance
  • Latched head design to enable ease of access to optics for maintenance


Discover Acoem’s case studies

Why do you need DSL-460 ?

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

Request pricing

Connect with Acoem

Contact us to learn more about our solutions, services, and training programs.

Would you like to…?