Understanding relative humidity and relative saturation - HPP272

HPP272 User Guide

Document code
M211972EN
Revision
G
Language
English
Product
HPP272
Document type
User guide
Water and hydrogen peroxide have a very similar molecular structure, and they both affect the humidity of the air in which they are present. HPP272 measurement makes a difference between the humidity caused by both H2O2 vapor and water vapor, and the humidity caused only by water vapor:
  • Relative saturation is a parameter that indicates the humidity of the air caused by both H2O2 vapor and water vapor. When relative saturation reaches 100 %RS, the vapor mixture starts to condense.
  • Relative humidity is a parameter that indicates the humidity of the air caused only by water vapor.
Figure 1. Effect of H2O and H2O2 on relative saturation (RS) and relative humidity (RH)
1
Space without H2O2 vapor. When H2O2 vapor is not present, relative saturation equals relative humidity.
2
Same space with H2O2 vapor introduced. Relative saturation is higher than relative humidity.

During H2O2 bio-decontamination processes, it is often important to monitor the possibility of condensation. For this purpose, it is not enough to know the level of relative humidity (RH), because RH only indicates the humidity caused by water vapor. The possibility of condensation is affected by the combined humidity of H2O2 vapor and water vapor, which is why you need to monitor relative saturation (RS).