Industrial Opacity Monitors
Environmental Monitor Service (EMS) designs and manufactures industrial opacity monitors for continuous measurement of visible emissions, smoke and dust in stacks and ducts. Since 1990, facilities worldwide have relied on EMS for accurate, serviceable monitoring systems, U.S.-based technical support and genuine replacement parts.
EMS offers single-pass and dual-pass opacity monitors for process control, Title V monitoring and applications that require U.S. EPA Performance Specification 1. Available systems support physical path lengths from 2 to 50 feet, depending on the model and application.
Choose the Right Opacity Monitor
- EMS WatchDog dual-pass opacity monitor — a rugged industrial system for 3–50 ft paths, with PS-1 and ASTM D6216 performance, analog outputs, programmable relays and MODBUS communications.
- EMS WatchDog 800 single-pass opacity monitor — a compact, economical system for 3–8 ft paths and dependable process-control or alarm applications.
- EMS WatchDog PS-1 continuous opacity monitoring system — a dual-beam system with automatic zero and span functions, a 5.7-inch touchscreen, trends and diagnostics for EPA PS-1 applications.
- EMS Guardian smoke opacity detector — a straightforward 2–8 ft single-pass detector with selectable alarm settings for cremation equipment, incinerators, boilers and combustion furnaces.
Choosing the correct opacity monitor depends on the permit requirement, stack or duct dimensions, expected opacity range, installation environment and required outputs. Request an EMS application review and quote for model-selection assistance.
EMS WatchDog
- Dual-pass industrial opacity and dust measurement
- Meets or exceeds U.S. EPA 40 CFR Part 60, Appendix B, PS-1 and ASTM D6216
- Physical path lengths from 3 to 50 ft
- Measures opacity, optical density and configured dust-concentration values
- Two configurable 4–20 mA outputs, six programmable relays and MODBUS over RS-485
- NEMA 4 optical hardware with through-the-lens alignment and automatic LED aging compensation
EMS WatchDog 800
- Single-pass opacity monitor with an electronically modulated green LED
- Physical path lengths from 3 to 8 ft (91–244 cm)
- Opacity measurement range from -100% to 100%
- One 4–20 mA analog output and a 2 A alarm relay
- NEMA 4X controller, 24 VDC operation and CE, UL and cUL approvals
- Ideal for boilers, baghouses, ducts, fan control, oven and diesel exhaust, cremation equipment and other process applications
Single-Pass vs. Dual-Pass Opacity Monitors
A single-pass monitor sends light once across the process opening from an emitter to a detector. It is often a practical choice for shorter paths and process-control applications. A dual-pass, or double-pass, opacity monitor sends light to a reflector and back to the transceiver. Dual-pass systems can support longer paths and are available for applications that require EPA Performance Specification 1. Read the full single-pass vs. double-pass opacity monitor comparison.
Industrial Opacity Monitor Applications
EMS opacity and dust monitors are used wherever operators need continuous information about visible emissions or changes in particulate loading. Common applications include:
- Boiler stacks and combustion furnaces
- Baghouse and electrostatic precipitator monitoring
- Industrial incinerators and cremation equipment
- Cement kilns and process manufacturing
- Ductwork, fan control and filtration systems
- Oven, diesel and other industrial exhaust
Because permit and process requirements vary, EMS reviews the application, physical path length, mounting arrangement, environment, desired alarm points and communication needs before recommending a system.
Accuracy, Maintenance and Compliance
Reliable opacity data depends on both the instrument and the installation. Correct alignment, clean optical surfaces, dependable purge air, appropriate zero and span checks, and routine preventive maintenance help protect data accuracy and extend monitor life. Facilities subject to regulatory requirements must also follow their permit, applicable test methods and required quality-assurance procedures.
EMS provides opacity monitor repair, field service, startup, alignment and certification support, including PS-1 audit services and neutral-density filter certification. Current manuals, data sheets and dimensional forms are available on the EMS Documents and Forms page.
EMS was the original equipment manufacturer for the Rosemount OPM 3000, OPM 4000 and OPM 4001. Learn about OEM replacement parts, factory repair and direct replacement systems for Rosemount OPM opacity monitors.
Frequently Asked Questions
What is an opacity monitor?
An opacity monitor measures the reduction in transmitted light caused by smoke, dust or other particulate matter in a stack or duct. The reading is typically expressed as percent opacity and can be used for process control, alarm functions, reporting and regulatory compliance.
Which EMS opacity monitor should I choose?
The WatchDog 800 is a compact single-pass option for 3–8 ft paths. The standard WatchDog is a versatile dual-pass monitor for 3–50 ft paths. The WatchDog PS-1 adds a color touchscreen, automated calibration functions and expanded diagnostics for EPA PS-1 continuous opacity monitoring applications. The Guardian provides straightforward smoke-opacity alarm capability for 2–8 ft paths.
Does every application require a PS-1 opacity monitor?
No. The correct requirement depends on the facility’s permit and applicable regulation. Process-control and smoke-alarm applications may not require a PS-1 system. EMS can help identify the appropriate product, but the facility should confirm its regulatory obligations with the permitting authority.
How often should an opacity monitor be serviced?
Service frequency depends on the application, environment, purge-air quality and regulatory program. Operators should inspect alignment and optical cleanliness regularly, respond promptly to diagnostic or calibration changes, and follow the maintenance and audit schedule in the product manual and facility permit.
Opacity Monitor Resources
- How do opacity monitors work?
- How to choose an industrial opacity monitor
- Single-pass vs. double-pass opacity monitors
Need help selecting an opacity monitor? Request a quote from EMS or contact our technical team to discuss your application.