Quick answer: The testo 310 measures flue-gas quantities for combustion service. Confirm the exact sensor and instrument generation, zero as directed, record stable oxygen and carbon-monoxide readings and interpret them against the appliance specification—not a universal target.
What makes the testo 310 different
The testo 310 is a compact combustion analyzer intended for routine heating service. Its compact field workflow differs from the 300 touchscreen/reporting platform; printer availability and accessory packages depend on the set. For related guidance, see testo 300 Combustion Analyzer: Setup, O₂/CO Readings and Reports.
Prepare and carry out the measurement
- Verify that a qualified technician has confirmed the appliance operating safely and identified an approved sampling point.
- Inspect the flue-gas probe, sampling hose, condensate protection and sensor status; complete fresh-air zeroing exactly as specified in the corresponding manual.
- Select the actual fuel and operating mode, and record burner load, flue/combustion-air temperatures and other installed sensor channels.
- Sample at the specified point with proper probe placement, wait for stable O₂ and CO and save the values together with the operating condition.
Model-specific use and interpretation
Check the fitted flue probe and condensate trap, zero in clean air and choose the actual fuel. Wait for steady operation before reading O₂ and CO, then document draft and temperatures only where the instrument/set supports those measurements. For related guidance, see 320 Combustion Test Setup: Interpreting O₂ and CO Readings.
O₂ indicates residual oxygen, CO indicates incomplete-combustion product and flue temperature supports the calculated flue-loss estimate. A calculated combustion-efficiency percentage is not seasonal appliance efficiency. Sensor configuration and fuel choice change what can be displayed. For a broader explanation of these measurements, see flue-gas readings explained.
Use measured CO for safety interpretation and calculated combustion efficiency only as the specific flue-loss estimate—not a claim about annual heating costs.
Worked example (hypothetical)
Hypothetical record: at one stable burner condition O₂ is 5.2%, CO 18 ppm and flue temperature 150 °C. At another condition the values are 4.7%, 26 ppm and 165 °C. The changes are -0.5 percentage points O₂, +8 ppm CO and +15 °C; they cannot be judged safe or optimal without appliance criteria and comparable load conditions.
If the readings change unexpectedly
- Recheck probe location, blocked sampling hose, condensate trap, sensor zero and the fuel setting before concluding that combustion changed.
- If O₂ and CO drift together, review appliance operating state and combustion-air supply under an approved service protocol.
- If there is unsafe CO, spillage, incomplete combustion or any hazard indication, stop the measurement and follow the applicable emergency and professional service procedures.
A compact visit without the wrong accessories
The testo 310 is often used for a quick service check. Identify whether the supplied set includes a printer and the required flue-gas probe before promising printed documentation. Start with a stable appliance, perform fresh-air sensor zeroing as instructed, and compare readings at one stated firing condition. If readings drift, check condensate handling and sampling-line integrity before assuming a combustion change.
Interpretation: An efficient record includes the appliance, chosen fuel, sensor readings, time, CO hazard response and whether a printer was actually used. For the documentation fields that support this record, see the guide to a boiler combustion test report.
Limits and safety
Follow the exact instrument manual and the equipment manufacturer’s acceptance criteria. The example is not field evidence, a legal limit or a commissioning target. Work on energized electrical equipment, combustion systems, charged refrigerant circuits or hot surfaces requires qualified personnel and the site’s approved protective procedures.