johnson matthey logo



Exhaust Monitors

This page features descriptions and literature for:

• HAPGuard™

• CRT® dm

• SootAlert® Monitor




As an owner/operator of stationary engines, you know Johnson Matthey represents the highest quality in emission control systems. Johnson Matthey developed the HAPGuard™ monitor to complement our Modulex™ HAPs converters, the latest line of our modular catalytic converter and converter-silencers. The HAPGuard monitor is easy to use and has been engine-tested for proven performance.

Continuous monitoring of exhaust temperature and pressure ensures that your Johnson Matthey Modulex catalytic converter or converter-silencer stays in compliance with the latest RICE NESHAP regulations.

hapguard exhaust monitor

HapGuard Monitor advantages:

  •  Alerts operator if the pressure drop across the catalyst is not within 2" w.c. of the value established during initial testing at 100% load

  •  Warns operator if the catalyst inlet temperature is out of the EPA-specified range for rich burn and lean burn engines:
          •  Rich Burn: 750° F < TCATALYST INLET < 1250° F
          •  Lean Burn: 450° F < TCATALYST INLET < 1350° F

  •  Proven technology, engine-tested
  •  State-of-the-art electronics, battery back-up
  •  User-friendly
  •  Simple, easy to read data panel
  •  Removable memory; stores up to 5 years of data


Download information below for the HAPGuard™ Monitor in PDF format:

hapguard exhaust monitor literature

Hapguard™ Exhaust Temperature & Pressure Monitor
Sales Bulletin



CRT®dm & RDM
CRT Diagnostic Module & Remote Display Module

Johnson Matthey's CRT®dm is a premier device that provides operational feedback to ensure optimal emission reduction.

The CRT®dm is the only device on the market to offer extended data-logging capabilities and the ability to store up to 24 months of consecutive data. It continuously logs exhaust temperature and backpressure while the engine is running.

CRTdm diagnostic module

CRT®dm Features:

  •  Alerts user of routine filter maintenance condition, engine upset conditions, and tracks data for easy system troubleshooting
  •  High speed RS-232 communications supports alarm programming, troubleshooting and downloading data
  •  User-friendly software for Windows 95 and later PC Laptops
  •  Two alarm outputs, with the ability to light the vehicle's check/stop engine light, control an audible alarm (if equipped), and derate or shut down electronically controlled engines
  •  Ruggedly packaged; operates over a wide temperature range, and logs temperature and pressure data
  •  Customer programmable alarm settings
  •  Four LEDs for local feedback during installation and troubleshooting

CRTdm diagnostic module



Download information below for the CRT®dm & RDM in PDF format:

CRTdm diagnostic module literature

CRT®dm Diagnostic Module & RDM Remote Display Module
Sales Bulletin

SootAlert® Monitor

Each time you run your engine, Johnson Matthey's unique SootAlert® Monitor checks the time, pressure, and temperature of the CRT system, and shows you a green Light when the filter is clean, a yellow Light when it has begun to accumulate soot, and a red Light indicating that it is time to regenerate the CRT Filters.

Johnson Matthey's CRT System is sized for each engine application to allow for a minimum of 24 consecutive cold starts before filter regeneration is necessary (30 minutes per cold start) and 150 cold starts before cleaning ash from the filter is necessary. This means that an engine can be run once a month for a half-hour at idle or minimal load and not need to be regenerated for two years.

SootAlert monitor


Regenerating the filters is easy—just run the engine under the recommended load until the Soot Alert light turns from red to green, and the CRT system is good for another 24 cold starts. This method also conforms to most engine manufacturers' recommendations to run the engine under load periodically to maintain the engine and to avoid wet stacking.