Hydrogen Cyanide Gas Sensor: Case Study by Sensorix GmbH

This article originally appeared in the AWE International Magazine

In this case study we are pleased to present our solution path and describe all the steps we needed to extend the measuring range of our hydrogen cyanide gas sensor as per to customers’ requests.


We received two different requests from customers. One customer needed an HCN sensor for a larger measuring range which is also qualified for high temperatures. For the other customer, the most important factor was that the gas sensors are specified up to 50°C. If not, there was a risk that this customer’s factory might have to be shut down due to high outdoor temperatures.

What was special about this request:

In general, this sensor class with organic electrolytes is specified up to a temperature of 40°C. This is because the electrolyte can evaporate. And the warmer it is, the faster the evaporation. At some point, there is no electrolyte left and the whole system does not work anymore. This raises the question of how quickly the sensor is damaged by high temperatures, whether this is a problem in principle, or whether it can be tolerated for a short period of use.


Various tests were carried out to validate the extended specification. Firstly, we tested the sensor’s behaviour with regard to zero current and sensitivity at elevated temperatures. We also tested the sensor’s aging behaviour under these extended conditions. For this purpose, we first stored the sensors at 50°C and regularly checked the reaction to the target gas. Furthermore, we simulated an exhaust pipe with a 50°C air flow, which causes the electrolyte of the sensors to evaporate faster.


The tests have shown that the product meets the customers’ requirements and can be used at up to 50°C for a short time. The sensor provides good readings, and the zero current is within the acceptable range. However, since the electrolyte evaporates faster at high temperatures, we recommend that this type of sensor should not be used permanently at a temperature of 50°C, but only for a short time.

It is important to note that the product has not been technically changed. We considered the customer’s needs and specified the sensor for a wider temperature range. The same applies to the measuring range: We have successfully tested the linearity up to 50 ppm and the continuous load at 50 ppm. This allows our customer to use the HCN sensor without hesitation even at expected HCN concentrations of 40 or 50 ppm.


If possible, we will test and validate all products for the extended temperature range so that the customer has greater possibility and flexibility for use. In our datasheet, you will find all information about the product’s performance under the defined conditions.