Engine-specific menus on the Testo 350 take the guesswork out of testing. Simply select the rich-burn or lean-burn engine application, and the 350 will take care of the rest. For example:

  • Rich-burn engine exhaust, when uncontrolled, can have wide concentration ranges, and both CO and NOx can fluctuate significantly. The on-board CO dilution system will automatically configure for optimum engine testing, perfect for a rich burn engine.

  • Lean-burn engines have different exhaust characteristics, but NO2 can still make up a significant portion of the total NOx measurement, which is why the 350 measures both NO and NO2 for proper lean-burn engine setup.

Measuring Capabilities

O2 NO Hydrocarbons
CO NOlow Velocity
COlow NO2 Pressure
NOx SO2 Temperature
CO2 H2S Dilution

In addition, the patented dilution system extends sensor ranges (specifically needed for engine testing) and provides greater sensor protection. It also gives a true CO measurement, while eliminating the cross-sensitivity problems other analyzers exhibit in their CO measurements.


Active gas conditioning is mandatory for EPA and High-Accuracy testing. The integrated gas conditioning system (thermoelectric cooler with automatic condensate removal pump) on the 350 delivers dry-basis data as required for most reporting, while the powerful sample pump automatically controls sample flow rate for EPA accuracy.

The 350 engine probe covers all engine testing needs, with features including: 

  • Pressure relief hose allows easy testing right or left cylinder banks

  • Teflon-lined sample hoses ensure the highest level of accuracy

  • Optional thermocouples enable stack temperature measuring

  • Optional sintered filters handle heavy particulate loading from diesels

  • Optional heated sample lines for EPA testing

  • Optional hi-temp probe shaft lets you test any engine

  • 9 ft. hose extensions available (5 extensions maximum)

No matter your engine testing requirement, the 350 is tool you need.



Simultaneous catalyst measurements used to mean using an expensive and complex trailer-mounted testing rig. Not anymore. With the 350, multiple analyzers can be linked together to read catalyst measurements.

Simply connect two or more (up to 16) probes and analyzer boxes to the exhaust stack (each analyzer can be configured to test either pre- or post-catalyst exhaust gas). Then just connect the analyzer boxes using a data cable, and you can read real-time measurements from each box on a single hand-held control unit. Even display two measurements side-by-side. And when you finish testing, use Testo easyEmission software to analyze and export your readings. 




From combustion tuning to compliance testing data, easyEmission provides extraordinary data management capabilities. See the power of an intuitive user interface and exclusive features, including:

  • Real-time monitoring window, allowing testing in the background

  • Export data to Microsoft Excel or create a PDF

  • Clear, graphical information display

  • Generate testing reports

  • Calculate maximum, minimum, and average values

  • User-defined reports and printouts

  • Manage data by customer and site location

  • Control your 350 via Bluetooth