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Fieldpiece SOX3 Combustion Checker with Auto Pump

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The Fieldpiece SOX3 Combustion Checker with Auto Pump is a great tool to easily tune furnaces when a complete combustion analysis isn’t necessary—designed specifically for HVACR pros. The SOX3 provides all the essential measurements needed to adjust most combustion equipment. It measures %O2 and flue temperature and calculates %CO2, %Excess Air, and combustion efficiency.

The SOX3 Fieldpiece Combustion Analyzer tool was designed to help HVACR professionals do more with their devices. From custom fuels to field-replaceable O2 sensors. The SOX3 can be trusted to measure up for any furnace tuning job. Also, the pump works automatically. There’s no hand pumping, and techs can pause the pump anytime to save battery life. Furthermore, the SOX3 Oxygen Sensor indicators tell techs when a new sensor is needed. Moreover, with calibration data stored on the sensor, it can be swapped out in seconds (field-replaceable), so you never need to send your instrument in for calibration. The threaded R-cone holds the barrel firmly in the flue.

The strong magnet on the back of the SOX3 holds the device firmly to the side of the chimney while the internal electric pump does all the work. Techs view the results on the triple line display (hands-free testing). Quickly calculated and displayed on the screen, the SOX3’s combustion efficiency calculation is an excellent measurement to help determine the health of a furnace. Not only does the SOX3 test Natural Gas, Oil #2, and Propane, but it can be quickly and easily programmed to test any fuel. So non-conventional furnaces are just as easy to tune as conventional furnaces.


  • (1) Fieldpiece SOX3 Combustion Analyzer
  • (1) Barrel and Thermocouple Handle - RSOX3
  • (1) Threaded Barrel Lock - RCONE2
  • (1) Filter accessory kit - RAOX9
  • (1) Padded, Blow-molded Case


  • Fieldpiece SOX3 Combustion Check
  • Automatic Electric Pump with Pause
  • Field-replaceable Oxygen Sensor
  • Measures flue temp and %O2
  • Calculates %CO2, %EA, and Combustion Efficiency
  • Hands-free Testing with magnet, R-cone, and automatic pump
  • Programmable for Custom Fuel types


Fieldpiece SOX3 Combustion Check
Sensor Type : Highly accurate oxygen sensor
Operating environment : 32 to 122°F (0 to 50°C) at <75% R.H.
Storage environment : -4 to 140°F (-20 to 60°C) at <80% R.H. with battery removed from meter
Temperature Coefficient : 0.1 times the applicable accuracy per ° from 32°F to 64°F and 82°F to 122°F (0 to 18°C and 28 to 50°C)
Battery : 9V
Battery Life : 28 hours typical alkaline
Auto Power off : After 15 minutes
Accuracy : Stated accuracy at 23°C±5°C, <75% R.H.
Dimensions : 45.0mm(H) x 69.8mm(W) x 211.7mm(D)
Weight : approx. 579.7g with battery
Display : 4 digit liquid crystal display(LCD) with maximum reading of 9999
Low battery indication : The low battery icon is displayed when the voltage drops below the operating level
Range : -58°F to 1000°F (-50°C to 538°C)
Resolution : 0.1°
Accuracy : ±[0.6%+3°F(1.7°C)]after field calibration.
Sensor Type : Rod K-type thermocouple.
Range : -50°F to 900°F (continuous operation range) up to 1000°F (single exposure use)
Accuracy : (±4°F) on -50°F to 545°F (±0.75%) on 545°F to 1000°F
Oxygen Range : 0 to 25%
Accuracy : ±0.3%O2 (Calibrated at 72°F, 20.9%O2)
Max Overload : 30% Oxygen
Operational temp range : -4°F to 122°F
Response time : Under 2 minutes


Q & A

Can the sox3 be used on oil furnaces?

Yes, it can dial in any equipment that has a flue.

Does it have any type of alarm or buzzer when O2 levels drop below a breathable level?

No, that is not consistent with the purpose or use of the device. This is used for a few minutes and when adjustments are completed it is removed.

How long should I run the furnace before performing any tests with the fieldpiece sox3?

You should wait 10-15 minutes after turning it on.

Customer Reviews

Based on 1 review
Lawrence Ring
Great tool good value

Easy to read and operate and has a good battery life.