vH2O2 Vapor Concentration & Condensation Point

This blog is the fourth in a 4-part series where we describe how process parameters influence vaporized hydrogen peroxide bio-decontamination applications.

First blog: Humidity, condensation point, and maximum achievable vH₂O₂

Second blog: H₂O₂ Solution Concentration Ratio, Condensation Point & Maximum Achievable vH₂O₂

Third blog: Temperature, Condensation Point & Maximum Achievable vH₂O₂ ppm in Bio-decontamination

In this series, we propose four basic process parameter rules.  This blog focuses on the 4th rule: 

Increasing the H₂O₂ vapor concentration decreases the amount of water vapor the air can hold, and therefore, condensation occurs sooner.

In Figure 7 (from our white paper), we can see that increasing the H₂O₂ vapor concentration decreases the amount of water vapor the air can hold and condensation occurs sooner.

Image

Each point in Figure 7 is a condensation point, meaning that Relative Saturation is 100 %. Temperature is on the x axis and ppm vH₂O₂ is on the y axis. The curve in the graphs shows the maximum relative humidity at a given temperature and concentration of ppm vH₂O₂.

As shown, at 20 °C and 300 ppm hydrogen peroxide, relative humidity will be 60% and relative saturation will be 100%. If we increase vH₂O₂ to 600 ppm at 20 °C, relative humidity is then 39 % and relative saturation is 100 %.

By increasing the air temperature to 40 °C with vH₂O₂ concentration at 300 ppm, relative humidity will be 87% and relative saturation will be 100%. The higher the temperature, the more water vapor the air can hold; relative humidity is increased.

To summarize our proposed rules for controlling condensation in vaporized hydrogen peroxide bio-decontamination applications: 

• Lowering the initial level of humidity increases the amount of H₂O₂ vapor that can be used before condensation.
• Increasing the temperature increases the amount of water and hydrogen peroxide vapor the air can hold, thereby increasing the maximum achievable ppm vH₂O₂.
• A higher concentration H₂O₂ solution increases the H₂O₂ vapor that can be used before condensation.
• Increasing the H₂O₂ vapor concentration decreases the amount of water vapor the air can hold, and therefore, condensation occurs sooner

Conclusion

Over this series of blogs (based on our white paper), we have demonstrated how an in-depth understanding of the relation between critical process parameters allows for the development of effective, repeatable vH₂O₂ bio-decontamination cycles.

Single-parameter measurement is often insufficient for monitoring and ineffective for process control. We have also shown why relative saturation is an important value in accurately predicting condensation. This is why Vaisala’s unique PEROXCAP® technology measures multiple parameters in a single sensing unit, including: hydrogen peroxide vapor ppm, temperature, dew point, vapor pressure, and humidity as both relative humidity and relative saturation.

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