Video Q&A - Humidity sensors in VH2O2 applications

Vaporized Hydrogen Peroxide Sensor
Life Science
In this video, we answer questions received during our webinar "Humidity sensors in VH2O2 applications: Choosing the right sensor."
Thank you to all who attended and sent these questions we didn't have time to answer during the live webinar.
For a quick summary of the webinar's recommendations, fast forward to 7:30 where Joni explains how to ensure you've selected the right sensor for your application.
The webinar is free to view on demand. Please find the transcript of the questions and answers in this video below.
Leave any comments or questions in the fields below and we will reply by email!
Joni: As we already covered in the webinar, we can use humidity products in an environment where we have vaporized hydrogen peroxide, such as this HMD62 for measuring humidity and temperature, for example, or the HMP7. But if we really want to control a process and measure relative saturation and hydrogen peroxide ppm values, we need to use the HPP270 probe. Here I have it connected to the Indigo201 transmitter.
Sanna: Thank you Joni. Let's go to the questions. First question: How is the PEROXCAP® sensor (of the HPP270 series probes) calibrated?
Both the HPP271 and the HPP272 probes are delivered with a certificate that contains calibrations for relative saturation, relative humidity, vaporized hydrogen peroxide, temperature, and analog outputs as well. We have here [at Vaisala calibration centers] a humidity calibration station and a vaporized hydrogen peroxide calibration station. Both of these are traceable to SI units (International System of Units).
Joni: The next question was: How often should these instruments be calibrated?
Sanna: That is an excellent question. The typical interval is once per year, but naturally, [the calibration interval] depends on the use of the sensor. The more the sensor is exposed to hydrogen peroxide vapor, the more often it is recommended to send the probe in for calibration.
Joni: The third question was: Can I use salt calibrator for calibrating these instruments?

Yes, and I happen to have here an HMK15 Vaisala salt calibrator that can be used for calibrating this HPP272 probe, as well as these other humidity products. For this, you will need a USB cable, a laptop, and the Insight PC software, which is available as a free download on our website.
Sanna: So, like Joni said, that this is a good way to do on-site calibration for humidity and for vaporized hydrogen peroxide using this equipment. But naturally, you can also send your probe to Vaisala device for calibration.
Joni: Another question was: How many sensors do I need in my isolator, especially if it’s a big isolator? So, the first consideration here is the temperature differences there are in the application. If you have a uniform temperature and good circulation in the application, then one probe is good enough.
But if there are temperature differences, then you need to know the lowest temperature if you want to avoid condensation, and you will need a temperature sensor at that cold spot.  In the webinar, we also cover this mixture dew point temperature, which is a very valuable parameter to have in this kind of application, because when the mixture of dew point temperature is close to the lowest temperature in your application, you are at risk of condensation.
Sanna: Ok next question: Does the catalyzed H2O2 have an influence on the humidity measurement? Yes, it does. So if you have a catalytic HUMICAP® sensor and the vaporized hydrogen peroxide is catalyzed into water vapor and oxygen, then there is extra humidity that is seen by the sensor. This is taken into account by the HPP271 and HPP272 measurement algorithm. 
Joni: Another question was about the different methods of producing vaporized hydrogen peroxide. A person asked: Is the Vaisala sensor suitable for different vapor generator technologies, such as nebulization for example. The answer is yes. The HPP270 series of probes measures vaporized hydrogen peroxide is independent of how the hydrogen peroxide vapor is produced.
Sanna: OK, and then there was a question how the HUMICAP® and PEROXCAP® sensors function in high humidity. In Vaisala we test our sensors extensively and the PEROXCAP® sensor is designed to function in high humidity, even if there is visible condensation on the walls. And Joni can explain this technology further…
Joni: Yes, PEROXCAP® is designed to be used in condensing environments. The sensor is actually heated up. So even in condensing environment, the HPP270 probes are capable of measuring humidity levels and vaporized hydrogen peroxide.
Sanna: The same applies to the HMP7 technology, it has a warmed probe for measuring humidity. If you have further questions about how we test these elements of our sensor technology, please contact us.
We’ve covered all the questions that we received. But before we go, we will go over the different sensors we covered and how you select the right sensor according to your application’s environment.
Joni: So the first question you need to ask is, does my application contain hydrogen peroxide vapor and if the answer is no, then you are free to choose from many of our humidity products. But if the answer is yes, you have hydrogen peroxide in your application, you would choose from the HPP270 series probes.
Then you would ask: Do I want to control the decontamination process? And if the answer is no, then you need to decide, is this hydrogen peroxide ppm exposure regular or is the concentration is very low, roughly below four hundred ppm? If the answer is no, you are good with HUMICAP® sensors that are equipped with a catalytic layer on the sensor. But if the answer is yes, you would benefit from having the catalytic HUMICAP with the chemical purge function. 
But, back to the question of controlling the bio-decontamination process… if the answer is yes, you want to control the process, then the next question is: is there uncertainty due to temperature differences?
If the answer is no, your application has a very stable temperature, then the HPP272 is good for that application. But if there is high variability in temperature, you would want additional temperature measurements and focus on the  mixture dew point parameter, also measured with the HPP272.
Thank you Joni! And thank you for joining us.

The full webinar can be viewed at any time. 
If you have further questions about Vaisala’s vaporized hydrogen peroxide technology, please contact us.

New Webinar Vaporized Hydrogen Peroxide Calculations & Formulas

In this webinar, we discuss the methods for calculating different humidity and vaporized hydrogen peroxide variables, such as: relative saturation, parts per million, and mixture dew point temperature. A better understanding of these variables can help you to take this knowledge into practice, such as calculating VH2O2 concentrations in different types of bio-decontamination processes.

Learn more

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