Two points of view. Two ways of seeing calibration of Instrument Odour Monitors (in short here, o-sensors). The 29th and 30th of August, the Working Group (WG) 41 committed to the new standard on o-sensors, met in Berlin, Germany to discuss a bit more about the text. This time, there were some very hot discussions on the interesting issue of o-sensor calibration. The tense atmosphere was broken from time to time by the pause for coffees, but all in all, everybody was enjoying the fascinating discussions being hold in the meeting room of the Institute for Materials Research and Testing in Berlin.
Like in tennis matches, the ball went from one side to the other side of the court. The question is the following: Could a non-specific o-sensor be used on any application? That is, could an o-sensor that is performing fine in a composting site, be used also in an oil refinery? In that case, is there any way to prove that the quality of the results is transferable? should we define procedures to calibrate o-sensors on site? Which is the Certified Reference Material (CRM) to calibrate the o-sensor? is it possible to design a CRM for quality procedures? These and more questions were addressed during these 2-day meetings.
There are two kinds of o-sensor vendors: the goodies and the baddies. Both sell o-sensors for many applications, but one of them follows the (would be) EN standard on Instrumental Odour Monitoring and the other one doesn't. One of them will invest time and economic resources for a better product and the other one will not. This is one of the reasons why standards are for, to define the filter between good and bad practices.
Now, who defines what is right or wrong? in this case an open group formed by over 20 experts from different fields and different European countries who reach to a set of standards through consensus. However, consensus was at stake this time. That is why an important part of the task group dedicated to o-sensor calibration met in the last ISOEN conference in Montreal. After that meeting in Montreal, a document was produced and sent to the WG. Three months later, the content of this document was discussed in Berlin.
As mentioned before the essence of this document is that it is important to consider at least two different types of situations for instrumental odour monitoring: o-sensors that are designed and provided directly connected to the final application/user and 'multi-purpose' instruments that are designed and provided to be used in different situations, which are not specifically defined at the moment the instrument is installed.
According to the EN 14181, there are three Quality Assurance Levels (QAL):
- QAL1 relates to the certification of the instrument. The QAL 1 sets a procedure to demonstrate that the o-sensor is suitable for the intended purpose before installation.
- QAL2 is the calibration against the standard reference method (in this case dynamic olfactometry). This is made on-site.
- QAL3 determines whether zero and span drift are within defined limits along the time. This is usually made through the Continuous Quality Assurance Procedure of the operator
These quality assurance levels are set for Automatic Measuring Systems (AMS), however the o-sensors are a very specific type of AMS. Do the o-sensors need to comply with these three QAL? This and more questions are being addressed at this moment. The final answer?... well as mentioned, there is no consensus yet ;-).
Here a picture of the whole team:
If your country is not represented in this Working Group (WG), why don't you join in? you can get access to the around 100 documents of this WG2. There is always a place here for any person interested on this subject. Feel free to contact your national standardization body in the case of CEN members to get in touch with this group. Even if you are not European, you can get access to all the documentation published in this group, provided that your country has an organization member of the ISO. Just contact your national representative body and ask them to link you to the CEN Technical Comittee 264 Working Group 41. You are more than welcome!
If you find this article interesting, you might also be interested in these articles:
- First Meeting of the CEN group dealing with gas sensors and pattern recognition.
- II Meeting of the CEN group dealing with gas sensors and pattern recognition for odorant monitoring in Nimes, France
- A new European Norm for e-noses?
- Considerations on Sampling and Measurement of Odours (VDI 3880 & VDI 3885/1) and eNoses
- 4th meeting of the CEN Working Group for 'Instrumental odour monitoring'