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Where is it found?
Hydrogen cyanide (HCN) is a colorless, highly volatile and flammable liquid that evaporates quickly. It occurs both naturally and as a result of industrial activities.
It is found in mines, specifically gold mining operations; combustion processes, such as vehicle exhaust and biomass burning; and industrial applications, especially in the production of plastics (like acrylonitrile), synthetic fibers, dyes, pesticides and electroplating.
Why measure it?
HCN is extremely toxic due to its interference with the body's ability to use oxygen. Acute exposure can lead to headache, dizziness, nausea, confusion, rapid breathing and loss of consciousness. High concentrations can cause seizures, respiratory failure, cardiac arrest and death within minutes. Besides, long-term, low-level exposure can lead to neurological problems, respiratory issues and thyroid dysfunction.
Due to its high toxicity and volatility, hydrogen cyanide is classified as a highly hazardous air pollutant and is strictly regulated in occupational and environmental settings.
HCN cartridge
The HCN cartridge features an integrated electrochemical sensor capable of detecting both low concentrations of HCN (below 1 ppm) and higher levels, up to 50 ppm, with an accuracy of ± 0.10 ppm. However, the HCN sensor exhibits significant cross-sensitivity to SO2 and NO2.
To ensure maximum accuracy when high concentrations of NO2 and SO2 are expected, it is recommended to use NO2, O3 and SO2 cartridges alongside the HCN cartridge. This setup allows the Kunak algorithm to compensate for cross-sensitivity and deliver more precise measurements.
Technical specifications
| Type | Electrochemical |
| Unit of measurement | mg/m3, ppm |
| Measurement range (1) | 0–50 ppm |
| Resolution (2) | 0.01 ppm |
| Operating temperature range (3) | -20 to 45 °C |
| Operating RH range (4) | 0 to 99 %RH |
| Recommended RH range (5) | 15 to 90 %RH |
| Operating life (6) | > 24 months |
| Guarantee range (7) | 200 ppm |
| Limit of Detection (LOD) (8) | 0.02 ppm |
| Repeatability (9) | 0.03 ppm |
| Response time (10) | < 160 sec |
| Typical accuracy (12) | ± 0.1 ppm |
| Typical precision R2 (11) | — |
| Typical slope (11) | — |
| Typical intercept (a) (11) | — |
| DQO - Typical U(exp) (13) | — |
| Typical intra-model variability (14) | < 0.1 ppm |
- 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.
