Vaisala HPP272 User manual

M211972EN-B
User Guide
Vaisala PEROXCAPâHydrogen Peroxide,
Humidity and Temperature Probe
HPP272

PUBLISHED BY
Vaisala Oyj
Street address: Vanha Nurmijärventie 21, FI-01670 Vantaa, Finland
Mailing address: P.O. Box 26, FI-00421 Helsinki, Finland
Phone: [phone]
Visit our Internet pages at www.vaisala.com.
© Vaisala 2017
No part of this manual may be
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displayed in any form or by any
means, electronic or mechanical
(including photocopying), nor
may its contents be modified,
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disclosed to a third party without
prior written permission of the
copyright holder. Translated
manuals and translated portions
of multilingual documents are
based on the original English
versions. In ambiguous cases, the
English versions are applicable,
not the translations.
The contents of this manual are
subject to change without prior
notice.
Local rules and regulations may
vary and they shall take
precedence over the information
contained in this manual. Vaisala
makes no representations on this
manual’s compliance with the
local rules and regulations
applicable at any given time, and
hereby disclaims any and all
responsibilities related thereto.
This manual does not create any
legally binding obligations for
Vaisala towards customers or end
users. All legally binding
obligations and agreements are
included exclusively in the
applicable supply contract or the
General Conditions of Sale and
General Conditions of Service of
Vaisala.
This product contains software
developed by Vaisala or third
parties. Use of the software is
governed by license terms and
conditions included in the
applicable supply contract or, in
the absence of separate license
terms and conditions, by the
General License Conditions of
Vaisala Group.

Table of Contents
1. About This Document................................................................................... 5
1.1 Version Information.......................................................................................... 5
1.2 Related Manuals................................................................................................ 5
1.3 Documentation Conventions...........................................................................5
1.4 Trademarks........................................................................................................ 6
1.5 Patent Notice.....................................................................................................6
2. Product Overview........................................................................................... 7
2.1 Introduction to HPP272....................................................................................7
2.2 Basic Features and Options.............................................................................8
2.3 Safety..................................................................................................................8
2.4 ESD Protection.................................................................................................. 9
2.5 Measured Parameters.......................................................................................9
2.5.1 Understanding Relative Humidity and Relative Saturation................10
2.6 Probe Filter........................................................................................................11
2.7 Chemical Purge.................................................................................................11
2.8 Environmental Compensation for Pressure..................................................12
2.9 Measurement Filtering Factor........................................................................12
2.10 Connectivity to Vaisala Insight Software......................................................12
2.11 Additional Features with Indigo Transmitters..............................................13
3. H2O2Measurement....................................................................................... 14
3.1 Operating Principle of H2O2Measurement.................................................. 14
3.2 Typical Applications........................................................................................ 16
3.3 Condensation Monitoring...............................................................................18
4. Installation.......................................................................................................20
4.1 Wiring...............................................................................................................22
4.2 Power Supply.................................................................................................. 23
4.3 Setting Probe in Analog or Digital Mode.....................................................23
5. Operation......................................................................................................... 25
5.1 Probe Start-Up................................................................................................25
5.2 Behavior at Exposure to H2O2.......................................................................25
5.3 H2O2Concentration Reading When Not Exposed to H2O2.......................25
5.4 Modbus............................................................................................................ 26
5.5 Operation in Analog Mode............................................................................ 26
5.5.1 Analog Output Overrange Behavior.....................................................26
5.5.2 Triggering Purge in Analog Mode......................................................... 27
6. Vaisala Insight Software............................................................................ 28
6.1 Connecting to Insight Software....................................................................28
Table of Contents
1

7. Using Probe with Indigo Transmitters................................................. 29
7.1 Indigo Overview............................................................................................. 29
7.1.1 Wireless Configuration Interface Overview.........................................30
7.2 Attaching Probes.............................................................................................31
7.3 Connecting to Wireless Configuration Interface........................................ 32
7.4 Logging in to Wireless Configuration Interface..........................................33
8. Maintenance....................................................................................................34
8.1 Cleaning the Probe.........................................................................................34
8.1.1 Chemical Tolerance.................................................................................34
8.2 Calibration and Adjustment.......................................................................... 35
9. Troubleshooting............................................................................................ 36
9.1 Problems and Their Possible Solutions........................................................36
9.2 Analog Output Error State............................................................................40
10. Technical Data.................................................................................................41
10.1 Dimensions......................................................................................................43
10.2 Accessories..................................................................................................... 44
Appendix A: Modbus Reference........................................................................45
A.1 Default Communication Settings................................................................. 45
A.2 Function Codes...............................................................................................45
A.3 Data Encoding................................................................................................ 45
A.3.1 32-Bit Floating Point or Integer Format...............................................45
A.3.2 16-Bit Integer Format............................................................................. 46
A.4 Modbus Registers...........................................................................................46
A.4.1 Measurement Data Registers.................................................................47
A.4.2 Configuration Registers......................................................................... 48
A.4.3 Status Registers...................................................................................... 54
A.4.4 Device Identification Objects.................................................................56
A.4.5 Test Value Registers................................................................................ 57
A.5 Modbus Communication Examples..............................................................58
Warranty........................................................................................................................ 61
Technical Support...................................................................................................... 61
Recycling....................................................................................................................... 61
HPP272 User Guide M211972EN-B
2

List of Figures
Figure 1 HPP272 Probe Parts...........................................................................................7
Figure 2 Eect of H2O and H2O2on relative saturation (RS) and
relative humidity (RH).....................................................................................10
Figure 3 Operating principle of PEROXCAP measurement................................... 15
Figure 4 Example behavior of H2O2concentration, relative
saturation (RS), and relative humidity (RH) in a
vaporized H2O2bio-decontamination cycle (non-
condensing conditions)...................................................................................17
Figure 5 Example: RS behavior in dierent temperatures when
H2O2concentration (500 ppm) and H2O concentration
(8850 ppm) are constant............................................................................... 18
Figure 6 Decontaminated space with dierent temperatures and
RS levels (H2O2and H2O concentration evenly distributed)................ 19
Figure 7 Probe M12/5 Pins..............................................................................................22
Figure 8 Wiring Example for Connecting HPP272 to a PLC in
Analog Mode..................................................................................................... 23
Figure 9 Pins on the M12 male connector.................................................................. 24
Figure 10 Connecting Probe to Insight.........................................................................28
Figure 11 Attaching Probes to Indigo............................................................................31
Figure 12 Enabling and Accessing Indigo's Wireless Configuration
Interface..............................................................................................................32
Figure 13 Indigo Login View............................................................................................ 33
Figure 14 HPP272 Dimensions........................................................................................ 43
List of Figures
3

List of Tables
Table 1 Document Versions..............................................................................................5
Table 2 Related Manuals....................................................................................................5
Table 3 Applicable Patents or Applications.................................................................6
Table 4 Available Parameters...........................................................................................9
Table 5 Measurement Performance..............................................................................41
Table 6 Inputs and Outputs............................................................................................42
Table 7 Mechanical Specifications............................................................................... 43
Table 8 Operating Environment....................................................................................43
Table 9 Spare Parts and Accessories.......................................................................... 44
Table 10 Default Modbus Serial Communication Settings...................................... 45
Table 11 Modbus Function Codes.................................................................................. 45
Table 12 16-bit Signed Integer Format Details........................................................... 46
Table 13 Modbus Measurement Data Registers (Read-Only).................................47
Table 14 Modbus Configuration Data Registers (Writable)....................................49
Table 15 Modbus Status Registers (Read-Only)........................................................ 54
Table 16 Error Codes in Register 0201hex (32-bit)..................................................... 55
Table 17 Error Codes in Register 0203hex (32-bit).................................................... 56
Table 18 Device Identification Objects......................................................................... 56
Table 19 Test Value Registers...........................................................................................57
HPP272 User Guide M211972EN-B
4

1. About This Document
1.1 Version Information
This document provides instructions for installing, using, and maintaining Vaisala PEROXCAPâ
Hydrogen Peroxide, Humidity and Temperature Probe HPP272.
Table 1 Document Versions
Document
Code
Date Description
M211972EN-B December 2017 This document. Added description and Modbus registers for
pressure compensation, removed restriction not to perform a
purge during H2O2exposure, clarified operating system
requirements for Vaisala Insight software, clarified Indigo
200 transmitter compatibility with HPP272.
M211972EN-A September 2017 First version.
1.2 Related Manuals
Table 2 Related Manuals
Document Code Name
M211887EN Hydrogen Peroxide, Humidity and Temperature Probe HPP270 Series Quick
Guide
M211877EN Indigo 201 Analog Output Transmitter User Guide
1.3 Documentation Conventions
Warning alerts you to a serious hazard. If you do not read and
follow instructions carefully at this point, there is a risk of injury or even death.
WARNING!
Caution warns you of a potential hazard. If you do not read and
follow instructions carefully at this point, the product could be damaged or
important data could be lost.
CAUTION!
Chapter 1 – About This Document
5

Note highlights important information on using the product.
Tip gives information for using the product more eciently.
Lists tools needed to perform the task.
Indicates that you need to take some notes during the task.
1.4 Trademarks
Vaisalaâ, HUMICAPâ, and PEROXCAPâare registered trademarks of Vaisala Oyj.
Indigo™is a trademark of Vaisala Oyj.
All other product or company names that may be mentioned in this publication are trade
names, trademarks, or registered trademarks of their respective owners.
1.5 Patent Notice
This product is protected by the following patents and patent applications and their
corresponding national rights:
Table 3 Applicable Patents or Applications
Issuing Oce Publication Number
European Patent Oce EP 3004868
State Intellectual Property Oce of the P.R.C. CN 105229463A
United States Patent and Trademark Oce US 20160084811
HPP272 User Guide M211972EN-B
6

2. Product Overview
2.1 Introduction to HPP272
Vaisala PEROXCAPâHydrogen Peroxide, Humidity and Temperature Probe HPP270 series is
designed for demanding hydrogen peroxide bio-decontamination processes. The probes are
suitable for a variety of applications such as isolator, material transfer hatch, and room bio-
decontamination.
Hydrogen Peroxide, Humidity and Temperature Probe HPP272 provides measurement for
vaporized H2O2concentration, relative saturation, relative humidity, and temperature.
The H2O2measurement is based on comparing the readings of two composite humidity
sensors to determine the vapor concentration of H2O2. The probes are easy to install with a
plug-in/plug-out M12/5 connection. The digital and analog output options include an RS-485
interface for Modbus communication and two current output channels.
The probe is not intended for safety level measurement.
The probe is not intended to be used in vacuum applications.
When there is H2O2in the probe's environment, the probe must
always be powered on. When powered on, the PEROXCAP sensor is heated,
which permits using the probe in condensing H2O2conditions, maintains
measurement performance, and lengthens the probe's lifetime. When the probe
is powered o, exposure to H2O2condensation can break the PEROXCAP sensor
within a day, and the sensor will not recover.
CAUTION!
21 543
6
Figure 1 HPP272 Probe Parts
1Yellow transport cap. Remove this cap
before using the probe.
2Filter covering the sensor. The filter is
an essential part of the measurement
technology: do not remove the filter.
Filters are available as spare parts.
3PEROXCAP sensor under the filter.
4H2O2and humidity probe.
5Temperature probe.
65-pin M12 connector.
Chapter 2 – Product Overview
7

More Information
‣Dimensions (page 43)
‣Operating Principle of H2O2 Measurement (page 14)
‣Installation (page 20)
‣Wiring (page 22)
2.2 Basic Features and Options
• Vaisala PEROXCAPâH2O2measurement technology with excellent long-term stability.
• Vaporized H2O2measurement range 0 ... 2000 ppm.
• Relative saturation (RS) measurement range 0 ... 100 %RS.
• Relative humidity (RH) measurement range 0 … 100 %RH.
• Temperature (T) measurement range +5 ... +70 °C.
• Robust design allowing the probe to be installed directly in the process environment.
When powered on, the probe withstands H2O2and H2O condensation. The probe also
withstands nitrogen gas.
• Protective filter over the sensors designed to withstand high air flow rates and turbulence.
• Sensor heating to avoid condensation on the sensors.
• Chemical purge for optimized performance and lifetime.
• Pressure compensation for H2O2concentration (ppm), H2O concentration (ppm), and
relative saturation (%RS) measurement.
• Digital output: RS-485 interface for Modbus communication.
• Analog output: 2 x 4 ... 20 mA (default).
• Easy plug-in, plug-out.
• Can be used as a stand-alone probe or with Vaisala Indigo 200 series transmitters.
• Can be connected to Vaisala Insight software for configuration, diagnostics, and
temporary online monitoring.
More Information
‣Technical Data (page 41)
2.3 Safety
Ground the product and verify installation grounding periodically
to minimize shock hazard.
WARNING!
When returning a product for calibration or repair, make sure it
has not been exposed to dangerous contamination, and is safe to handle
without special precautions.
WARNING!
HPP272 User Guide M211972EN-B
8

Do not attempt to open the probe body. There are no user
serviceable parts inside the probe body.
CAUTION!
2.4 ESD Protection
Electrostatic Discharge (ESD) can cause immediate or latent damage to electronic circuits.
Vaisala products are adequately protected against ESD for their intended use. However, it is
possible to damage the product by delivering an electrostatic discharge when touching,
removing or inserting any objects inside the equipment housing.
Avoid touching component contacts or connectors when working with the device.
2.5 Measured Parameters
Table 4 Available Parameters
Parameter Unit
Vaporized hydrogen peroxide concentration by
volume
ppm
Relative saturation (RS) (H2O + H2O2) %RS
Relative humidity (RH) (H2O) %RH
Temperature °C
Absolute hydrogen peroxide mg/m3
Absolute humidity (H2O) g/m3
Water concentration by volume ppm
Water vapor pressure hPa
Water vapor saturation pressure hPa
The probe provides both digital and analog outputs.
• In digital output mode, the probe outputs all the measurement parameters.
• In analog output mode, the probe outputs the readings of two measurement parameters
(one parameter in each analog output channel). These measurement parameters are
chosen at the time of ordering the probe, and you can change them using Insight
software and via Modbus. The probe is also compatible with Vaisala Indigo transmitters,
which provide the option of three analog output channels.
Chapter 2 – Product Overview
9

More Information
‣Understanding Relative Humidity and Relative Saturation (page 10)
‣Measurement Data Registers (page 47)
‣Configuration Registers (page 48)
‣Connectivity to Vaisala Insight Software (page 12)
‣Setting Probe in Analog or Digital Mode (page 23)
2.5.1 Understanding Relative Humidity and Relative Saturation
Water and hydrogen peroxide have a very similar molecular structure, and they both aect the
humidity of the air in which they are present. HPP272 measurement makes a dierence
between the humidity caused by both H2O2vapor 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
H2O2vapor 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.
%RH%RS
00
100100
H2O
H2O2
%RS %RH
0 0
100
100
H2O
1 2
Figure 2 Eect of H2O and H2O2on relative saturation (RS) and relative humidity (RH)
1Space without H2O2vapor. When H2O2vapor is not present, relative saturation equals
relative humidity.
2Same space with H2O2vapor introduced. Relative saturation is higher than relative
humidity.
During H2O2bio-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 aected by the combined humidity of H2O2vapor and water vapor, which is
why you need to monitor relative saturation (RS).
HPP272 User Guide M211972EN-B
10

2.6 Probe Filter
The white filter on the probe covers the PEROXCAP sensor. The filter is made of porous PTFE
that allows ambient air to reach the PEROXCAP sensor while protecting the sensor in strong or
turbulent air flow.
The filter is an essential part of the measurement. If the filter is
broken, dirty, or removed altogether, measurement does not work as intended.
• Do not touch the filter with bare hands. If you need to touch the filter, always
use clean gloves (rubber, cotton or similar material).
• Keep the filter free of any grease or oil.
• Do not touch any parts under the filter. Touching parts under the filter may
damage the sensors.
CAUTION!
More Information
‣Problems and Their Possible Solutions (page 36)
2.7 Chemical Purge
Chemical purge is a 4-minute process where the sensors are heated to remove possible
contamination. The purge is essential for the long-term performance and accuracy of the
probe in demanding H2O2environments. During the purge, only temperature measurement is
available.
The purge is automatically performed:
• At probe start-up.
• At intervals (default 24 hours, configurable between 1 hour ... 1 week using Vaisala Insight
software, Modbus, or Indigo 200 transmitters). Purge is postponed by 30 minutes if H2O2
is present or RH is not steady.
Purge is recommended at least every 24 hours of powered-on time, even if the probe has not
been continuously exposed to H2O2.
Optional: if needed, you can also trigger a purge manually with Modbus (in digital mode) or
pin #5 on the M12 connector (in analog mode).
More Information
‣Triggering Purge in Analog Mode (page 27)
‣Operation in Analog Mode (page 26)
Chapter 2 – Product Overview
11

2.8 Environmental Compensation for Pressure
When necessary, you can apply pressure compensation to improve the measurement accuracy
of the probe (probe software v.1.1.0 and later). The probe does not have on-board pressure
measurement, but a pressure reading from an external source can be used as a setpoint value
for compensation.
You can configure the pressure compensation parameters using Vaisala Insight software,
Modbus configuration registers, or an Indigo 200 transmitter.
By default, the pressure compensation is turned o. When the compensation is o, the probe
uses the default compensation value (1013.25 hPa).
Pressure compensation aects the following parameters:
• H2O2concentration (ppm)
• H2O concentration (ppm)
• Relative saturation (%RS)
More Information
‣Vaisala Insight Software (page 28)
‣Configuration Registers (page 48)
2.9 Measurement Filtering Factor
You can set a filtering factor that aects the speed at which the latest H2O2and RS
measurements are integrated into the output of the probe. This allows averaging the output if
the measuring environment produces occasional exceptionally high or low readings.
The filtering factor can be set either with Modbus configuration register 0308hex, Vaisala
Insight software, or an Indigo 200 transmitter.
By default, the filtering factor is set to 1.0, which means the latest measurement is shown
directly in the output, without any filtering. To apply filtering, enter a lower filtering factor to
include previous measurements in the calculation of measurement output. For example,
changing the filtering factor to 0.9 results in an output that is a combination of the latest
measurement (90%) and the previous measurement output (10%).
More Information
‣Configuration Registers (page 48)
2.10 Connectivity to Vaisala Insight Software
The probe can be connected to Vaisala Insight software using a Vaisala USB cable (no.
242659). With the Insight software, you can:
• See device information and status.
HPP272 User Guide M211972EN-B
12

• See real-time measurement.
•Configure serial communication settings, purge settings, filtering factor, and analog
output parameters and scaling.
More Information
‣Connecting to Insight Software (page 28)
2.11 Additional Features with Indigo Transmitters
The probes are compatible with Vaisala Indigo 200 transmitters starting from Indigo
transmitter serial number N4650357 (Indigo 200 transmitter software version 1.3.2 or higher).
Connecting the probe to an Indigo transmitter provides a range of additional options for
outputs, measurement viewing, status monitoring, and configuration interface access.
Examples of additional features available with Indigo transmitters include:
• 3.5” TFT LCD color display or non-display model with LED indicator
• Digital output or 3 analog outputs (depending on the transmitter model)
• 2 configurable relays
• Wireless browser-based configuration interface for mobile devices and computers (IEEE
802.11 b/g/n WLAN)
The selection of available additional features (for example, output and connectivity options)
varies depending on the Indigo transmitter model. For more information on Indigo
transmitters, see www.vaisala.com/indigo.
More Information
‣Indigo Overview (page 29)
Chapter 2 – Product Overview
13

3. H2O2Measurement
3.1 Operating Principle of H2O2Measurement
When there is H2O2in the probe's environment, the probe must
always be powered on. When powered on, the PEROXCAP sensor is heated,
which permits using the probe in condensing H2O2conditions, maintains
measurement performance, and lengthens the probe's lifetime. When the probe
is powered o, exposure to H2O2condensation can break the PEROXCAP sensor
within a day, and the sensor will not recover.
CAUTION!
PEROXCAPâsensor technology works using measurements from two Vaisala HUMICAPâ
sensors. HUMICAP sensors guarantee quality and reliability, with their reputation for
repeatability, accuracy, excellent long-term stability, and negligible hysteresis – even in the
most demanding high-concentration H2O2applications in atmospheric pressure.
HUMICAP sensor is a thin-film polymer sensor consisting of a substrate on which a thin
polymer film is deposited between two electrodes. The film absorbs or releases vapor
according to humidity changes in the environment. As the humidity changes, the dielectric
properties of the polymer film change, and so does the capacitance of the sensor. The
instrument’s electronics measure the capacitance of the sensor and convert it into a humidity
reading.
PEROXCAP measurement uses two composite HUMICAP sensors, one with a catalytic layer
and one without. The catalytic layer catalyzes H2O2from the vapor mixture. Therefore, the
HUMICAP sensor with this layer only senses water vapor, providing a measurement of partial
water pressure, i.e. relative humidity (RH). The sensor without the catalytic layer senses both
hydrogen peroxide vapor and water vapor in the air mixture. The dierence between the
readings from these two sensors indicates the vapor concentration of H2O2.
HPP272 User Guide M211972EN-B
14

H202
H20
2H20
02
2H202
H20
2
1
3
2
3
A B
Figure 3 Operating principle of PEROXCAP measurement
AHUMICAP sensor with a catalytic layer (under the probe filter). This sensor only senses
water vapor.
BHUMICAP sensor without a catalytic layer (under the probe filter). This sensor senses the
air mixture with both hydrogen peroxide vapor and water vapor.
1Catalytic layer over the thin film polymer. This layer catalyzes hydrogen peroxide into
water and oxygen and prevents it from entering the sensing polymer.
2Thin film polymer between two electrodes.
3Alumina substrate.
In addition to measuring vaporized H2O2concentration, HPP272 provides measurement for
relative saturation, relative humidity, and temperature. Relative humidity (RH) is a parameter
that indicates the humidity value derived from water vapor only, whereas relative saturation
(RS) indicates the humidity percentage derived from water vapor and H2O2vapor together.
When relative saturation reaches 100 %RS, the vapor mixture starts to condense.
Chapter 3 – H2O2 Measurement
15

3.2 Typical Applications
The probe is not intended for safety level measurement.
The probe is not intended to be used in vacuum applications.
Vaporized hydrogen peroxide is used for bio-decontamination in several applications from
healthcare and pharmaceutics to food and beverage industry. Vaporized hydrogen peroxide is
an easy-to-use and eective bio-decontaminating agent that destroys the full spectrum of
biological contaminants including micro-organisms such as bacterial spores, mycobacteria,
and non-enveloped, non-lipid viruses. Bio-decontamination with vaporized hydrogen peroxide
is a low-temperature, environmentally friendly process that leaves no real residues, only water
vapor and oxygen. One of the benefits also is that the bio-decontamination process can be
validated.
Common vaporized H2O2bio-decontamination applications include isolators, transfer hatches,
closed Restricted Access Barrier Systems, and room bio-decontamination (for example, in
hospital environments, cleanrooms, decontamination tents, aircrafts, ships, and shipping
containers).
The bio-decontamination process typically has the following phases:
1. Optional dehumidification, where relative humidity is decreased to a desired level, for
example, by warming the space.
2. Conditioning, where vaporized H2O2mixture is introduced into the space to be bio-
decontaminated.
3. Decontamination, where H2O2concentration is maintained at a desired level for a certain
time.
4. Aeration, where H2O2is removed from the bio-decontaminated space.
HPP272 User Guide M211972EN-B
16

100%
0%
More
Less
Cycle Phase
Aeration Decontamination Conditioning Dehumidification
CONDENSATION POINT
RELATIVE
SATURATION (RS)
RELATIVE HUMIDITY (RH)
VAPORIZED HYDROGEN
PEROXIDE CONCENTRATION
Humidity
H2O2
Concentration
Figure 4 Example behavior of H2O2concentration, relative saturation (RS), and relative humidity
(RH) in a vaporized H2O2bio-decontamination cycle (non-condensing conditions)
In the non-condensing bio-decontamination cycle example shown in Figure 4 (page 17):
• In the dehumidification phase, RH (and RS) decreases.
• When the conditioning phase starts, H2O2concentration rises rapidly. There is also a rapid
increase in RS, which indicates the humidity caused by both H2O2vapor and water vapor.
Because the generated H2O2vapor is typically mixed with water vapor, RH also starts to
rise.
• In the decontamination phase, H2O2concentration is steady. However, RS level rises slowly
close to 100 %RS, i.e. condensation point, due to rising RH level.
• In the aeration phase, H2O2concentration, RS, and RH all decrease. When H2O2
concentration is zero, RS equals RH.
The way your bio-decontamination process is designed aects which parameters you want to
measure in dierent phases.
Depending on your bio-decontamination process, you may also want to either create or avoid
condensation during the conditioning and decontamination phases. In these phases, the air in
the bio-decontaminated space always contains both water and H2O2vapor, which both aect
the possibility of condensation. To monitor and control whether and when condensation
forms, it is useful to know the combined humidity level of water vapor and H2O2vapor: relative
saturation (RS). When relative saturation reaches 100 %RS, the vapor mixture starts to
condense.
Chapter 3 – H2O2 Measurement
17

For condensation monitoring, choosing the right measurement location is very important. If
the bio-decontaminated space has surfaces with a lower temperature than where RS is
measured, condensation may start to form on those surfaces even before RS reaches 100 %RS
in the exact measurement location. To monitor the possibility of condensation, consider
installing the probe close to a surface where you suspect condensation may form.
More Information
‣Understanding Relative Humidity and Relative Saturation (page 10)
‣Installation (page 20)
3.3 Condensation Monitoring
H2O+H2O2vapor mixture starts to condense when relative saturation (RS) reaches 100 %RS.
RS level is strongly aected by temperature: decreasing the temperature increases RS. If there
are temperature dierences in the bio-decontaminated space, RS varies in dierent parts of
that space even if the H2O+H2O2vapor is evenly distributed.
Temperature
Relative saturation
21 21.5 22 22.5
100
95
85
90
H2O2= 500 ppm
H2O = 8850 ppm
Figure 5 Example: RS behavior in dierent temperatures when H2O2concentration (500 ppm) and
H2O concentration (8850 ppm) are constant
For condensation monitoring, this means that even if you measure < 100 %RS in one point, RS
may be 100 %RS in another, cooler point. The following figure shows an example of how RS
can vary in a decontaminated space according to temperature dierences.
HPP272 User Guide M211972EN-B
18