Expert advice on hydrogen peroxide vapor sensing

Vaporized Hydrogen Peroxide sensor structure
Industrial Manufacturing and Processes
Industrial Measurements
Life Science

In case you missed our recent webinar "Achieving Effective H2O2 Bio-decontamination in Facilities & Containment Systems" you can watch the recorded version.

During the webinar we received many questions we did not have time to answer. Our experts answered afterwards and here we share their advice on questions that are broadly under these three categories:

  • Vaporized Hydrogen Peroxide Sensors
  • Equipment, Materials and Structures
  • Biological Indicators


Vaporized Hydrogen Peroxide Sensors

QUESTION: When we use a typical RH sensor in the cycle development, do they measure Relative Humidity or Relative Saturation? In other words, does vaporized H2O2 affect the RH reading of typical RH sensors?

ANSWER: Water and hydrogen peroxide have a very similar molecular structure, and they both affect the humidity of the air, in which they are present. Therefore, a typical RH sensor without catalytic layer will have a greater humidity value than real saturation level of the air mixture is. So yes, the vaporized H2O2 does effect the typical humidity sensor and it will cause accelerated drift in the sensor with repeated exposure. The relative humidity sensor with a catalytic layer measures the humidity of the air caused only by water vapor. During H2O2 exposure the RH% value is lower than relative saturation RS% value. Learn more about relative saturation in this webinar.

Also, Vaisala offers some of our traditional RH/Temperature instruments with sensors that include a catalytic layer. This layer, along with our warmed probe technology and chemical purge features, can offer a real RH measurement with vaporized H2O2 present. Information on these other instruments:

Humidity and Temperature Probe HMP3

Humidity and Temperature Meter Series HMT330

Hydrogen Peroxide HPP270

Equipment, Materials and Structures

QUESTION:  Is vaporized H2O2 recommended over a fogging system?

ANSWER: The HPP270 series probes can be used to measure vaporized H2O2 in both cases.There are several variables to consider when choosing a system for bio-decontamination. Vaisala does not take a position on vaporizer or fogging systems. We provide sensing equipment for intelligent monitoring and control of critical processes. It’s best to speak with a system vendor to learn if the equipment will meet the needs of your applications.

QUESTION:  What equipment and MOC's (maintenance in operational condition) are generally used for H2O2 decontamination, including room construction, HVAC systems (including ducting seals)? I've seen the need for powered seals to block the return and supply ducts in a fermentation room because the air handler was not only connected to this room, but was at risk of returning vaporized hydrogen peroxide to other areas with occupants.

ANSWER: We recommend reviewing the resource materials we provided during the webinar for reference. That said, materials that can survive the corrosive effects that H2O2 condensation are needed.

QUESTION:  Could you comment on reports that vaporized H2O2 is absorbed by materials in the room or isolator then leaches out over time after aeration? This leaching effect could result in accumulation in under ventilated areas or inactivation of the product being manufacturing in the H2O2 fumigated facilities?

ANSWER: Thank you for the question, and while Vaisala is not in a position to comment of the results of vaporized H2O2 desorption may have, we do know that certain materials will absorb and release vaporized H2O2 at different rates and concentrations. Careful material selection for areas and items in the process, combined with sufficient aeration duration times can help to mitigate any potential latent effects. Proper cycle development for problem areas can include a post-aeration phase that might involve additional low level monitoring.

QUESTION:  In a laboratory that is decontaminated twice a year and the H2O2 is extracted via metal ductwork, what is the likelihood of the ductwork corroding over time?

ANSWER: There are too many variables to consider to provide a confident answer. The safe answer is to say that regular inspections should be performed if there is any danger of corroded ductwork to expose different areas to unsafe levels of the vaporized H2O2 being extracted.

Factors that would influence the likelihood of corrosion would be the concentration of vaporized H2O2 used in the process, any condensation occurring during the bio-decontamination cycle, or a risk of condensation in the ductwork of the laboratory. If the temperature of the exhaust duct is lower than the air being evacuated, there is a higher condensation and corrosion risk.

QUESTION:  Which is a better method of decontamination: Through Air Handling Unit or direct injection to the room?

ANSWER: It may be easier to use a vapor generator inside the room if there is only one room to be bio-decontaminated. Most of our customers use heat vaporization from a location integrated into the room or isolator. These vapor generators are easily controlled and the temperature differences are more easily managed.

Biological Indicators

QUESTION:  How do we select the location(s) for biological indicators for a bio-decontamination challenge study?

ANSWER: Although Vaisala does not sell biological indicators, we have seen that many of our customers put BIs in places they think will be most difficult to bio-decontaminate. A vendor of biological indicators can provide product specifications and guidance. However, there are people in sterilization services who offer their experience in blogs and other publications. Here is a blog from one service provider, Ardien Consulting. “The Rogue Biological Indicator.”

QUESTION:  Do you recommend placing Biological Indicators in triplicate to prevent "rogue" BIs? And would you suggest running BI's in duplicate or triplicate (in one location)?

ANSWER: Thank you for the question, but Vaisala is not in a position to provide guidance for products and methods that we are not directly involved with. I recommend reviewing the resource materials we provided with the webinar for reference. That said, we know that is commonplace to use duplicate BI’s to increase the assurance level, and triplicate BI’s can be used in more challenging areas.

Here are some reference materials available from various industry organizations, some are for purchase:


On-demand Webinar

Achieving Effective H2O2 Bio-decontamination
in Facilities & Containment Systems

In this webinar we discuss how bio-decontamination applications can benefit from vaporized hydrogen peroxide. You'll learn about the measurements that ensure the efficacy of bio-decontamination processes and why, including: ppm (H2O2), Relative Humidity, Relative Saturation, and Temperature.

Watch now

Case study: Proactively fighting superbugs with vaporized hydrogen peroxide

In this story, learn how Finnish OEM Cleamix created portable hydrogen peroxide vapor generators for efficient, cost-effective bio-decontamination.

“Bio-decontamination with vaporized hydrogen peroxide can be used proactively, not reactively. These pathogens are hard to kill and even harder to cure once a person is infected. Frequent bio-decontamination can stop outbreaks, but the equipment needs to be portable, highly efficient, and affordable...

 - Panu Wilska, CEO Cleamix Oyj




Jon Nottingham

May 18, 2020
Hello. I am sorry I missed the Webinar on your H2O2 sensor. I have a great deal of experience with H2O2 bio-deocontamination and would like to be kept informed of developments. I would also be happy to assist in answering the questions not directly connected to your equipment but more to the application of H2O2 decontamination.

Janice Bennett-Livingston

May 20, 2020
Hallo, thank you very much for your interest in our blogs and our vaporized hydrogen peroxide sensor! We are always interested in working with industry experts!

To ensure you receive updates, you can send us your email preferences here:

And you can always watch the recorded webinar:

Best regards,


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