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Where is it found?
Oxygen (O2) is an essential gas that makes up approximately 20.9% of the volume of atmospheric air at sea level. It is fairly evenly distributed throughout the troposphere and is vital for biological processes such as cellular respiration.
It is also present in many chemical compounds and plays a role in natural oxidation reactions, such as combustion and the decomposition of organic matter. Additionally, it dissolves in bodies of water, where it is crucial for aquatic life.
Why measure it?
Measuring oxygen levels is key to ensuring safe and healthy conditions in industrial, urban and natural environments. Concentrations below 19.5% may indicate oxygen-deficient atmospheres that are potentially hazardous to human life, while high levels above 23.5% significantly increase the risk of ignition and explosion, especially in the presence of flammable materials.
Abnormal concentrations can also signal combustion processes, gas leaks that displace oxygen, or ventilation system failures. From an environmental perspective, monitoring oxygen helps assess air quality and the dynamics of atmospheric exchange.
O2 cartridge
The oxygen cartridge includes a high-precision electrochemical sensor designed to measure typical concentrations in ambient air—around 20.9%—as well as small deviations caused by industrial processes, gas displacement or other atmospheric changes.
This cartridge is highly stable, equipped with an advanced algorithm for temperature and humidity compensation, and can operate for over four years under non-extreme conditions. Over time, a slight drift may occur, which can be easily corrected using the remote calibration tool available on the Kunak Cloud platform.
Technical specifications
| Type | Electrochemical |
| Unit of measurement | % |
| Measurement range (1) | 0–30% |
| Resolution (2) | 1 ppb |
| Operating temperature range (3) | 0.01% |
| Operating RH range (4) | -30 to 50 °C |
| Recommended RH range (5) | 0 to 99 %RH (short periods) |
| Operating life (6) | > 4 years |
| Guarantee range (7) | 50% |
| Limit of Detection (LOD) (8) | — |
| Repeatability (9) | — |
| Response time (10) | < 10 sec |
| Typical accuracy (12) | ± 3% |
| Typical precision R2 (11) | — |
| Typical slope (11) | — |
| Typical intercept (a) (11) | — |
| DQO - Typical U(exp) (13) | — |
| Typical intra-model variability (14) | 0.1% |
- Measurement range: Concentration range measured by the sensor.
- Resolution: Smallest unit of measurement that can be indicated by the sensor.
- Operating temperature range: Temperature interval at which the sensor is rated to operate safely and provide measurements. In the PM sensor Type A: -40 to 50 °C with heater (more information on this version on request).
- Operating RH range: Humidity interval at which the sensor is rated to operate safely and provide measurements.
- Recommended RH range: Recommended relative humidity range for optimal sensor performance. Continuous exposure outside the recommended range may damage the cartridge.
- Operating life: Time period during which the sensor can operate effectively and accurately under normal conditions.
- Guarantee range: Concentration range covered by Kunak's guarantee.
- LOD (Limit of Detection): Measured at laboratory conditions at 20 °C and 50% RH. The limit of detection is the minimum concentration that can be detected as significantly different to zero gas concentration, calculated according to the Technical Specification CEN/TS 17660.
- Repeatability: Measured at laboratory conditions at 20 °C and 50% RH. Closeness of the agreement between the results of successive measurements of the same measurand carried out under the same conditions of measurement, calculated according to the Technical Specification CEN/TS 17660.
- Response time: Time needed by the sensor to reach 90% of the final stable value.
- Typical precision – R2, slope and intercept: Statistics obtained between the device hourly measurements and reference instruments in field tests between -10 to +30 °C at different locations. For the type B PM sensor, the expected error for PM10 is higher in the presence of coarse particles.
- Typical accuracy: For criteria pollutants, this is the average Mean Absolute Error (MAE) obtained between the device hourly measurements and reference instruments for 1 to 8 months of field tests between -10 to +30 °C in different countries. For other pollutants, it is the expected error of the measurement at the reading.
- DQO - Typical U(exp): Data Quality Objective expressed as the Expanded Uncertainty in the Limit Value obtained between the device hourly measurements and reference instruments for 1 to 8 months of field tests between -10 to +30 °C in different countries, calculated according to the European Air Quality Directive 2024/2881 and the Technical Specification CEN/TS 17660. For the type B PM sensor, the expected error for PM10 is higher in the presence of coarse particles.
- Typical intra-model variability: Calculated as the standard deviation of the three sensor means in 1 to 8 months of field tests between -10 to +30 °C in different countries.
A, B, C, D superindex: The super indexes refer to different types of cartridges related to the same target pollutant but with different technical specifications.
