testo 330 – Advanced flue gas analyzer with O₂ and CO sensors

The testo 330 is an advanced flue gas analyzer designed to give HVAC/R professionals clear insights and reliable results in increasingly complex working environments. The large 5.5" IPS touchscreen with app-like interface guides you step by step through flue gas and efficiency measurements, minimizes setup time and reduces operating errors in the field.
This flue gas analyzer is equipped with an O₂ sensor and a high-performance CO sensor, making it ideal for commissioning, service and troubleshooting of gas and oil-fired systems. With measurement ranges tailored to typical combustion applications and automatic zeroing, the instrument delivers stable and accurate readings for O₂, CO, draught, efficiency, flue gas loss and more – even under demanding conditions. Robust design (IP40), a proven sensor platform developed by Testo and TÜV-tested flue gas probes ensure long-term reliability.
Thanks to its integrated Bluetooth interface, the testo 330 connects seamlessly to the testo Smart App and to up to four wireless probes, enabling remote control, second screen operation and the integration of temperature, differential pressure, CO and CO₂ measurements. Measurement data is stored in the large internal memory and can be synchronized via testo Smart Connect for centralized data management across jobs, devices and teams. A powerful rechargeable battery with fast USB-C charging provides up to 10 hours of operation, ensuring the analyzer is ready for a full working day.

O₂	Measuring range 0 to 21 Vol.%
Accuracy ±0.2 Vol.% ±1 Digit
Resolution 0.1 Vol.%

Measuring range

0 to 21 Vol.%

Accuracy

±0.2 Vol.% ±1 Digit

Resolution

0.1 Vol.%

CO (with H₂ compensation, with active dilution)	Measuring range 0 to 40000 ppm
Accuracy ±100 ppm or ±10 ±1 Digit
Resolution 1 ppm

Measuring range

0 to 40000 ppm

Accuracy

±100 ppm or ±10 ±1 Digit

Resolution

1 ppm

CO (without H₂ compensation, with active dilution)	Accuracy ±200 ppm or ±20 % of mv ±1 Digit
Resolution 1 ppm
Measuring range 0 to 20000 ppm

Accuracy

±200 ppm or ±20 % of mv ±1 Digit

Resolution

1 ppm

Measuring range

0 to 20000 ppm

Flue Gas NO	Measuring range 0 to 3000 ppm
Accuracy ±5 ppm (0 to 100 ppm) ±1 Digit ±10 % of mv (2001 to 3000 ppm) ±1 Digit ±5 % of mv (101 to 2000 ppm) ±1 Digit
Resolution 1 ppm
*(optional)

Measuring range

0 to 3000 ppm

Accuracy

±5 ppm (0 to 100 ppm) ±1 Digit

±10 % of mv (2001 to 3000 ppm) ±1 Digit

±5 % of mv (101 to 2000 ppm) ±1 Digit

Resolution

1 ppm

*(optional)

Flue Gas Draft	Measuring range -4.00 to +16 InH₂O / -9.99 to +40 hPa
Accuracy ±0.01 InH₂O (+0.04 to +1.20 InH₂O) ±1 Digit / ±0.02 hPa (+0.10 to +3.00 hPa) ±1 Digit ±1.5 % of mv (+1.20 to +16 InH₂O) ±1 Digit / ±1.5 % of mv (+3.01 to +40 hPa) ±1 Digit ±0.002 InH₂O (0 to 0.0 InH₂O) ±1 Digit / ±0.005 hPa (0 to 0.1 hPa) ±1 Digit
Resolution 0.00 InH₂O (Remaining Range) / 0.01 hPa (Remaining Range) 0.000 InH₂O (0 to 0.0 InH₂O) / 0.001 hPa (0 to 0.1 hPa)

Measuring range

-4.00 to +16 InH₂O / -9.99 to +40 hPa

Accuracy

±0.01 InH₂O (+0.04 to +1.20 InH₂O) ±1 Digit / ±0.02 hPa (+0.10 to +3.00 hPa) ±1 Digit

±1.5 % of mv (+1.20 to +16 InH₂O) ±1 Digit / ±1.5 % of mv (+3.01 to +40 hPa) ±1 Digit

±0.002 InH₂O (0 to 0.0 InH₂O) ±1 Digit / ±0.005 hPa (0 to 0.1 hPa) ±1 Digit

Resolution

0.00 InH₂O (Remaining Range) / 0.01 hPa (Remaining Range)

0.000 InH₂O (0 to 0.0 InH₂O) / 0.001 hPa (0 to 0.1 hPa)

Temperature	Measuring range -40° to 2192 °F / -40 to +1200 °C
Accuracy ±0.5 % of mv (Remaining Range) ±1 Digit ±0.9 °F (32° to 212.0 °F) / ±0.5 °C (0.0 to +100.0 °C) ±1 Digit
Resolution 1.0 °F (Remaining Range n2{+#0} {%S2}) / 1 °C (Remaining Range) 0.1 °F (-40° to 1831.8 °F) / 0.1 °C (-40 to +999.9 °C)

Measuring range

-40° to 2192 °F / -40 to +1200 °C

Accuracy

±0.5 % of mv (Remaining Range) ±1 Digit

±0.9 °F (32° to 212.0 °F) / ±0.5 °C (0.0 to +100.0 °C) ±1 Digit

Resolution

1.0 °F (Remaining Range n2{+#0} {%S2}) / 1 °C (Remaining Range)

0.1 °F (-40° to 1831.8 °F) / 0.1 °C (-40 to +999.9 °C)

Efficiency testing (η)	Measuring range 0 to 120 %
Resolution 0.1 %

Measuring range

0 to 120 %

Resolution

0.1 %

Flue gas loss	Measuring range 0 to 99.9 %
Resolution 0.1 %

Measuring range

0 to 99.9 %

Resolution

0.1 %

CO₂ (calculated from O₂)	Measuring range 0 to CO₂ max (Display range)
Accuracy ±0.2 Vol.% ±1 Digit
Resolution 0.1 Vol.%

Measuring range

0 to CO₂ max (Display range)

Accuracy

±0.2 Vol.% ±1 Digit

Resolution

0.1 Vol.%

Pressure measurement	Measuring range -40 to +80 InH₂O / -100 to +200 hPa
Accuracy ±1.5 % of mv (+100.1 to +200 ) ±1 Digit ±0.2 InH₂O (0.0 to +20.0 InH₂O) ±1 Digit / ±0.5 hPa (0.0 to +50.0 hPa) ±1 Digit ±1 % of mv (+20.0 to +40.0 InH₂O) ±1 Digit / ±1 % of mv (+50.1 to +100.0 hPa) ±1 Digit
Resolution 0.00 InH₂O / 0.01 hPa

Measuring range

-40 to +80 InH₂O / -100 to +200 hPa

Accuracy

±1.5 % of mv (+100.1 to +200 ) ±1 Digit

±0.2 InH₂O (0.0 to +20.0 InH₂O) ±1 Digit / ±0.5 hPa (0.0 to +50.0 hPa) ±1 Digit

±1 % of mv (+20.0 to +40.0 InH₂O) ±1 Digit / ±1 % of mv (+50.1 to +100.0 hPa) ±1 Digit

Resolution

0.00 InH₂O / 0.01 hPa

CO (without H₂ compensation)	Measuring range 0 to 5000 ppm
Accuracy ±10 % of mv (2001 to 5000 ppm) ±1 Digit ±5 % of mv (401 to 2000 ppm) ±1 Digit ±20 ppm (0 to 400 ppm) ±1 Digit
Resolution 1 ppm

Measuring range

0 to 5000 ppm

Accuracy

±10 % of mv (2001 to 5000 ppm) ±1 Digit

±5 % of mv (401 to 2000 ppm) ±1 Digit

±20 ppm (0 to 400 ppm) ±1 Digit

Resolution

1 ppm

Ambient CO	Measuring range 0 to 2000 ppm (internal/flue gas probe) 0 to 500 ppm (external with CO probe)
Accuracy ±10 ppm (30 to (500 ppm) ±1 Digit (external with CO probe) ±10 % of mv (101 to (2000 ppm) ±1 Digit (internal/flue gas probe) ±10 ppm (0 to 100 ppm) ±1 Digit (internal/flue gas probe) ±3 ppm (0 to (29 ppm) ±1 Digit (external with CO probe)
Resolution 1 ppm (external with CO probe) 1 ppm (internal/flue gas probe)

Measuring range

0 to 2000 ppm (internal/flue gas probe)

0 to 500 ppm (external with CO probe)

Accuracy

±10 ppm (30 to (500 ppm) ±1 Digit (external with CO probe)

±10 % of mv (101 to (2000 ppm) ±1 Digit (internal/flue gas probe)

±10 ppm (0 to 100 ppm) ±1 Digit (internal/flue gas probe)

±3 ppm (0 to (29 ppm) ±1 Digit (external with CO probe)

Resolution

1 ppm (external with CO probe)

1 ppm (internal/flue gas probe)

Differential Pressure 4 Pa measurement - Piezoresistive	Measuring range -50 to +0 InH₂O / -50 to +50 Pa
Accuracy ±0.0 InH₂O (< 0 InH₂O) ±1 Digit / ±0.3 Pa (< 10 Pa) ±1 Digit ±3.0 % of mv (Remaining Range) ±1 Digit
Resolution 0.0 InH₂O / 0.1 Pa

Measuring range

-50 to +0 InH₂O / -50 to +50 Pa

Accuracy

±0.0 InH₂O (< 0 InH₂O) ±1 Digit / ±0.3 Pa (< 10 Pa) ±1 Digit

±3.0 % of mv (Remaining Range) ±1 Digit

Resolution

0.0 InH₂O / 0.1 Pa

General technical data	Operating humidity 15 to +90 %rH (non-condensing)
Weight approximately 24 oz. / approximately 685 g
Dimensions approximately 9 x 4 x 2 in. (LxWxH) (incl. probe connection) / approximately 227 x 102 x 47 mm (LxWxH) (incl. probe connection)
Operating temperature 23° to 113 °F / -5 to +45 °C
Protection class IP40
Connectable probes 4 x digital Bluetooth® probe or testo Smart Probe; connectable: Smart Probes (°C, Delta P), CO + CO₂ probes
System requirements requires iOS 17 or newer; requires Android 14 or newer
Battery life 10 h
Display type 5.5" IPS touch display, HD 1280 x 720 pixels
Power supply Rechargeable battery, USB mains unit
Guarantee 48 + 12 months (with app registration)
Operating time ~60 min (25 °C)
Maximum ≤1,000,000 readings
Interface Bluetooth® 4.2
Radio range Up to 100 m (with no obstructions)
Battery charging option Quick charge
Battery charging time 20 min
Storage temperature -4° to 122 °F / -20 to +50 °C
Charging temperature 0 to +95 °F / 0 to +35 °C

Operating humidity

15 to +90 %rH (non-condensing)

Weight

approximately 24 oz. / approximately 685 g

Dimensions

approximately 9 x 4 x 2 in. (LxWxH) (incl. probe connection) / approximately 227 x 102 x 47 mm (LxWxH) (incl. probe connection)

Operating temperature

23° to 113 °F / -5 to +45 °C

Protection class

IP40

Connectable probes

4 x digital Bluetooth® probe or testo Smart Probe; connectable: Smart Probes (°C, Delta P), CO + CO₂ probes

System requirements

requires iOS 17 or newer; requires Android 14 or newer

Battery life

10 h

Display type

5.5" IPS touch display, HD 1280 x 720 pixels

Power supply

Rechargeable battery, USB mains unit

Guarantee

48 + 12 months (with app registration)

Operating time

~60 min (25 °C)

Maximum

≤1,000,000 readings

Interface

Bluetooth® 4.2

Radio range

Up to 100 m (with no obstructions)

Battery charging option

Quick charge

Battery charging time

20 min

Storage temperature

-4° to 122 °F / -20 to +50 °C

Charging temperature

0 to +95 °F / 0 to +35 °C

General technical data	Weight 136.86 oz. / 3880 g
Dimensions 20.5 x 15.7 x 5.1 in. (LxWxH) / 520 x 400 x 130 mm (LxWxH)
Housing Plastic
Product colour Black

Weight

136.86 oz. / 3880 g

Dimensions

20.5 x 15.7 x 5.1 in. (LxWxH) / 520 x 400 x 130 mm (LxWxH)

Housing

Plastic

Product colour

Black

General technical data	Diameter probe shaft 0.315 in. / 8 mm
Cable length 7.218 ft. / 2.2 m
Length probe shaft 7.087 in. / 180 mm
Product colour Black
Temperature maximum 932 °F / 500 °C
Diameter 0.2 in. / 6 mm
Weight 18.48 oz. / 524 g

Diameter probe shaft

0.315 in. / 8 mm

Cable length

7.218 ft. / 2.2 m

Length probe shaft

7.087 in. / 180 mm

Product colour

Black

Temperature maximum

932 °F / 500 °C

Diameter

0.2 in. / 6 mm