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Where is it found?
Hydrogen chloride (HCl) is a colourless to slightly yellow gas with a pungent odour. Upon contact with air, it forms dense, corrosive white vapours. It is naturally found in the digestive systems of most mammals and as a byproduct of various industrial processes. HCl is primarily used for synthesising inorganic and organic chemicals such as chlorine, ethylene dichloride and methyl chloride.
It is used in applications such as fumigation, electroplating, mining, chemical synthesis, and the production of synthetic fibres, plastics, dyes and pesticides.
Why is it harmful?
Hydrogen chloride is irritating and corrosive to any tissue with which it comes into contact. Brief exposure at low levels can irritate the skin, nose, eyes, throat and larynx, as well as cause eye and skin burns. Longer exposure causes syndromes of severe respiratory failure and death.
Its odour threshold was set at 0.77 ppm, while the irritating concentration has been reported as 33 ppm.
HCl cartridge
The hydrogen chloride cartridge has a built-in electrochemical sensor capable of monitoring low concentrations (< 1 ppm) as well as high concentrations of HCl, up to 20 ppm, with an accuracy of ± 0.1 ppm.
The HCl cartridge has a high cross-sensitivity with H2S. It is therefore recommended to use an H2S cartridge together with the HCl cartridge when high H2S concentrations are present (at ppm level), allowing the Kunak algorithm to correct this cross-sensitivity to obtain the highest precision.
The HCl cartridge is recommended for leak detection in industrial processes, and not for continuous HCl monitoring.
Technical specifications
| Type | Electrochemical |
| Unit of measurement | mg/m3, ppm |
| Measurement range (1) | 0–20 ppm |
| Resolution (2) | 0.01 ppm |
| Operating temperature range (3) | -20 to 50 °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) | 0.01 ppm |
| Repeatability (9) | 0.02 ppm |
| Response time (10) | < 45 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.
