`Reprinted from
`PHARMACEUTICAL ENGINEERINGE
`
`The Official Magazine of ISPE
`JanuaryIFebruary 2007, Vol. 27 No. 1
`
`Decontamination Methods
`
`
`The Physical Chemistry of
`Decontamination with Gaseous
`
`Hydrogen Peroxide
`
`by Carl Hultman, Aaron Hill, and Gerald McDonnell
`
`Introduction
`he decontamination of surfaces con-
`
`formaldehyde, ethylene oxide, or propylene
`oxide gas. An understanding of the physical
`chemistry behind the generation and control of
`gaseous hydrogen peroxide is important to op-
`timize the safety, efficacy, and reproducibility
`of a given decontamination process. This ar-
`ticle discusses the physical chemistry behind a
`typical process and the procedures needed to
`achieve optimal decontamination using gas-
`eous hydrogen peroxide.
`
`taminated with microorganisms within
`critical, enclosed areas is an important
`consideration to pharmaceutical, re-
`search, and other facilities. A safe and reliable
`way to decontaminate hard surfaces (including
`those in isolators, laminar flow cabinets, and
`cleanrooms) involves exposing the surfaces to
`gas-phase hydrogen peroxide.“3 Gas phase
`hydrogen peroxide is a known rapid, broad-
`spectrum antimicrobial which, as part of a
`Liquid and Gaseous
`controlled process, can allow for reproducible
`Hydrogen Peroxide
`Hydrogen peroxide (H202) is widely used as an
`area decontamination. Hydrogen peroxide also
`antiseptic, disinfectant, and sterilant.4 It is a
`has a rather safe profile, both from a user and
`desirable biocide because it demonstrates broad
`environmental perspective, in comparison to
`
`traditional fumigation methods that have used spectrum antimicrobial activity, has low toxic-
`
`This article
`
`reviews the
`
`physical
`
`chemistry of the
`
`safe production
`
`of hydrogen
`
`peroxide vapor
`and how to
`
`maintain a
`
`constant
`
`concentration of
`
`the vapor in a
`chamber. This
`
`article also
`
`reviews the
`
`calculations and
`
`procedures used
`to obtain the
`
`maximum
`
`concentration of
`
`vapor without
`
`allowing
`condensation of
`
`liquid to occur.
`
`Figure 1. Hydrogen
`peroxide vaporization
`processes.
`
`H20 + H202
`
`
`
`Liquid
`
`O
`
`O Vapor
`
`
`
`
`
`
`o /
`
`— H
`
`ot Surface
`
`Flash Vaporization
`
`Evaporation
`
`©Copyright ISPE 2007
`
`JANUARY/FEBRUARY 2007
`
`PHARMACEUTICAL ENGINEERING
`
`1
`
`Regeneron Exhibit 1051.001
`
`

`

`
`
`
`
`Decontamination Methods
`
`
`
`
`Hydrogen Peroxide Weight
`(%wlv)
`t = 25 C
`
`Vapor
`1.87
`8.0
`24.1
`35
`56.4
`
`Liquid
`32.1
`55.7
`73.9
`77.8
`88.3
`
`alloys, and stellite #6, act as catalysts that accelerate the
`decomposition of peroxide and also may encourage combus-
`tion when in contact with other materials. Lubricants such as
`
`silicones, paraffin, and aroclors also are Class 4 materials.
`Highly concentrated solutions of peroxide also may degrade
`certain electrical components or other materials; an example
`is that liquid hydrogen peroxide can attack the plasticizers in
`PolyVinyl Chloride (PVC), thus making the surface brittle
`after extended exposure. Additionally, certain grades of stain-
`less steel, such as 804 grade, can show slight corrosion or
`discoloration for liquid peroxide solutions ranging from 10 to
`100% by weight.
`
`Hydrogen Peroxide
`Evaporation and Condensation
`Hydrogen peroxide vapor can be conveniently produced from
`hydrogen peroxide/water solutions by two distinct processes,
`evaporation and flash vaporization - Figure 1. It is important
`to note that both processes will produce different concentra-
`tions of hydrogen peroxide vapor in a given volume. When
`liquid hydrogen peroxide is allowed to evaporate into a dry,
`enclosed space, the concentration ofhydrogen peroxide in the
`vapor state is much lower than the concentration in liquid
`state - Figure 2. This occurs because the water leaves the
`mixture at a higher rate than the peroxide due to the higher
`vapor pressure of water. For instance, if a 85% (by mass)
`hydrogen peroxide/65% water mixture evaporates into a dry
`enclosed space at 25°C, the resulting gas will consist of2.15%
`(by mass) hydrogen peroxide and 97.85% water at saturation.
`Saturation refers to the point at which the air can not hold
`further peroxide/water and at which point condensation (or
`precipitation) or water/peroxide will occur. The concentra-
`tion at which this occurs (referred to as the ‘dew’ point) can be
`predicted based on the peroxide/water concentrations, and
`the temperature ofthe gas -Figure 2. A detailed discussion of
`this phenomenon is discussed in the literature.5
`The evaporation rate can be increased by applying an
`energy source, for example heat can be applied to boil the
`peroxide/water solution. Since water has a lower boiling
`point than hydrogen peroxide, the water will vaporize at a
`higher rate, giving a higher concentration of water in the
`gaseous state and an increased concentration of hydrogen
`peroxide in liquid state. With time, the higher peroxide liquid
`concentration may become unsuitable for materials in con-
`tact with the liquid and can pose a safety risk.
`The equilibrium concentration of peroxide in the vapor
`over a liquid is always lower than the concentration in the
`liquid. Table 1 shows the concentration of peroxide in the
`vapor over liquid solutions at different peroxide concentra-
`tions at 25°C. The equilibrium concentration of peroxide in
`the vapor is always lower because the water escapes the
`liquid at a higher rate than the peroxide. The reverse is true
`when peroxide/water vapor condenses to the liquid state. As
`shown in Table A, the equilibrium concentration of the liquid
`formed when a vapor of35% by weight peroxide condenses is
`about 77.8% by weight peroxide. This is because the peroxide
`in the vapor has a greater desire to enter the liquid state than
`
`Table A. Equilibrium concentrations of hydrogen peroxide vapor
`that will form (evaporate) over liquid hydrogen peroxide (see
`Figure 1, Evaporation).
`
`ity, and breaks down into water and oxygen in the environ-
`ment. For example, liquid hydrogen peroxide solution is used
`directly on the skin at up to 6% w/v and at higher concentra-
`tions as a general surface disinfectant. Pure hydrogen perox-
`ide exists as a liquid at room temperature (25°C) and atmo-
`spheric pressure (101.85kPa). For antimicrobial applica-
`tions, greater efficacy is observed as the concentration is
`increased, which is particularly important to achieve spori-
`cidal activity; however, at high concentrations, liquid hydro-
`gen peroxide is unstable/reactive and may be explosive or
`undergo spontaneous combustion depending on how it is
`handled?6 Therefore, liquid preparations are used at lower
`concentrations diluted in water (generally8 to 59% byweight)
`and often in synergistic formulations with other biocides
`(including peracetic acid). The antimicrobial activity of hy-
`drogen peroxide is dramatically increased when in a gaseous
`phase. For example, the efficacy of hydrogen peroxide against
`bacterial spores has been shown to be similar at a gaseous
`concentration of 1mg/L in comparison to ~400mg/L in liquid.5
`To generate the gas, it is necessary to heat liquid hydrogen
`peroxide, generally by flash vaporization on a hot surface that
`will be discussed in more detail. Under these gaseous condi-
`tions, even lower concentrations (~O.1mg/L) of peroxide are
`rapidly antimicrobial and may be used to achieve sporicidal
`activity.
`A further consideration in the comparison of liquid and
`gaseous peroxide is material compatibility; attention should
`be focused on two factors when considering surface contact:
`
`1. the effect of the material on the decomposition rate of the
`peroxide (therefore loss of activity)
`2. the effect of hydrogen peroxide on the material itself.
`
`With liquid hydrogen peroxide (of about 45% by weight or
`more), the possibility of forming detonatable mixtures on
`reaction with organic substances may exist. Commonly used
`materials have been categorized into four different classes
`according to the suitability of exposing these materials to
`liquid concentrations equal to or higher than 90% by weight
`of peroxide in water.7 Of note, Class 4 materials may cause
`decomposition of hydrogen peroxide, and particularly with
`concentrated liquid peroxide, cause damage to the surface or
`form explosive mixtures. Some of these Class 4 materials
`include wood products and polymers such as neoprene, buna
`rubber, silicone rubber, and tygon. These materials may
`undergo degradation and/or cause spontaneous combustion.
`Other Class 4 metals, including copper, lead, magnesium
`
`2
`
`PHARMACEUTICAL ENGINEERING JANUARY/FEBRUARY 2007
`
`©Copyright ISPE 2007
`
`Regeneron Exhibit 1051.002
`
`

`

`GAS 0 LIQUID
`
`
`
`
`LIQUID
`
`Line A
`
`
`&
`
`
`
`Ypfliquid) = 9Xp[{Xw2/RT}(B0 + B1(3 — 4Xw)
`+ B2(1 — ZXW) (5 — 6XW)]
`
`(4)
`
`where:
`
`-
`
`- PM”) is the vapor pressure of the peroxide in the vapor in
`atmospheres
`ngas) is the vapor pressure of water in the vapor in atmo-
`spheres
`- XI) and XW are the mole fractions of peroxide and water
`respectively in the liquid
`Y1) and YW are the activity coefficients for peroxide and
`water respectively in liquid solution
`
`-
`
`P°p and P°W are the equilibrium vapor pressures in atmo-
`spheres of pure peroxide and water respectively at the tem-
`perature of interest. B0, B1, and B2 are empirically deter-
`mined constants for hydrogen peroxide with the values shown
`below.
`
`B0 = -752 + 0.97t
`B1 = 85
`B2: 18
`
`t in degrees centigrade
`
`Vapor pressure data may be converted into gas phase concen-
`tration units of mg gas per liter using the ideal gas equation
`as shown below.
`
`mg/liter = P(Mol Wt)(1000 mg/g)/RT
`
`(5)
`
`The concentration in mg/liter calculated from equation five is
`the concentration at a given temperature that will cause
`condensation, where, P is pressure in atmospheres, Mol Wt
`is the molecular weight of the gas ofinterest in grams/mole,
`R is the ideal gas constant 0.082 latm/deg mole, and T is
`temperature (°K).
`
`Achieving Optimal Concentration of
`Peroxide in Vapor Form
`As more vapor at a composition of35% by weight peroxide is
`introduced into an enclosed chamber, the pressure and con-
`centrations of the peroxide/water vapor in the chamber will
`increase. Eventually, a high enough concentration (expressed
`in mg/liter) will be reached at the operating temperature to
`cause the undesirable condensation ofliquid in the chamber.
`The maximum allowable concentration of peroxide in the
`vapor that will not cause condensation may be calculated
`using Equations one through five. One of the complications
`associated with condensation is that undesirable high con-
`centrations of peroxide liquid solutions will be formed on
`surfaces. Also, as liquid condenses, it may not uniformly
`cover all solid surfaces which may lead to non-uniform disin-
`fection/sterilization of surfaces. Other complications associ-
`ated with condensation will be elaborated on in a later
`
`section. The gaseous state for hydrogen peroxide when used
`for decontamination is advantageous because:
`
`Decontamination Methods
`
`
`
`
`Weight Percent of Hydrogen Peroxide
`
`GAS
`
`
`
`Temperature{”C)
`
`25
`
`2
`
`.
`35
`
`v
`we
`
`100
`
`Figure 2. A representation of the Hydrogen Peroxide/Water Phase
`Diagram. The upper solid line indicates the point at which the gas
`mixture is formed (note higher concentrations at higher
`temperatures) and the lower solid line when liquid is present. Line
`A shows the conversion of 35% liquid peroxide/water mixture (at
`25°C) to vapor at ~2% peroxide. Line B shows the condensation
`of 35% gaseous peroxide/water mixture to liquid at ~78%.
`
`the water in the vapor. Therefore, the peroxide condenses at
`a higher rate than the water, causing the higher concentra-
`tion of peroxide in the resulting liquid.
`Flash vaporization is a distinct process which can be
`achieved by applying energy, e.g., by direct application of a
`peroxide/water mixture to a hot surface - Figure 1. Flash
`vaporization forces the water and hydrogen peroxide in the
`liquid solution to evaporate simultaneously, thereby produc-
`ing gaseous concentrations of water and peroxide at approxi-
`mately the same concentration as the starting liquid mix-
`ture. The gas concentration will stay constant as long as
`condensation does not occur. Table B shows the concentra-
`
`tions of hydrogen peroxide that will saturate the vapor and
`cause condensation. If the gas concentration is increased
`above saturation or if cooled to below the dew point, conden-
`sation will occur. For example, when condensation occurs
`with a gas at ~85% by weight peroxide it will condense as a
`liquid at ~77.8% by weight peroxide - Figure 2.
`
`Physical Chemistry
`The vapor pressures of gases over multi-component liquid
`solutions may be calculated using the following equations25'8'9
`
`Pp(g85) = Xp(liq)YpP0p
`
`Pw(gas) = Xw(liq)YwP0w
`
`Ywfliquid) = 9Xp[{(1-Xw)2/RT}(BO + B1 (1 — 4Xw)
`+ B2(1 — ZXW) (1 — 6Xw)l
`
`(1 )
`
`(2)
`
`(3)
`
`©Copyright ISPE 2007
`
`JANUARY/FEBRUARY 2007
`
`PHARMACEUTICAL ENGINEERING
`
`Regeneron Exhibit 1051.003
`
`

`

`
`
`Decontamination Methods
`
`
`
`
`
`
`
`Figure 3. Dropwise condensation on contaminated metal surface.
`
`1. Gas will have uniform contact with all exposed surfaces,
`thus assuring that all surfaces are uniformly decontami-
`nated.
`
`2. Gas will have uniform contact with surfaces with complex
`topographies. Examples include horizontal or vertical
`surfaces, cracks, and complex curvatures.
`
`8. Gas may be safely maintained in the chamber.
`
`4. Gas may be efficiently and quickly removed from the
`chamber at the end of a given decontamination time thus
`decreasing cycle time.
`
`As the antimicrobial efficacy increases with increased perox-
`ide concentration, it is desirable to get the peroxide concen-
`tration in the gas as high as possible in the chamber without
`having condensation occur. It is possible to calculate the
`maximum pressure (and/or concentration) ofperoxide (or mg/
`L of peroxide in the chamber) that will initiate condensation
`using Equations one through five by knowing:
`
`1. the concentration of the flash vaporized gas being used to
`fill the chamber
`
`2. the total pressure in the chamber
`
`8. the humidity in the carrier gas (e.g., air used to circulate
`gas into and out of the chamber showing the design of the
`decontamination system - Figure 4) and the decontamina-
`tion chamber
`
`As these equations can often be time consuming to do by
`hand, computer programs have been developed to calculate
`the optimum decontamination conditions for any given en-
`closed volume.10 Table B shows examples of the maximum
`peroxide concentration allowed in the chamber to prevent
`condensation of liquid at various temperatures at two differ-
`ent humidity levels for the carrier gas. Calculations assumed
`flash vaporization of 85% by weight peroxide. Note that
`increasing the relative humidity in the carrier gas decreases
`the maximum concentration ofperoxide that may be achieved
`in the decontamination chamber.
`
`Why Condensation Should be Avoided
`As described above, high concentration of peroxide in the
`liquid state (as occurs with condensation) can be antimicro-
`bial, but also poses some further disadvantages. The first is
`material compatibility. As shown in Figure 1 and Table A, the
`concentration of a liquid formed when 85% by weight gas
`condenses will be about 78% by weight peroxide. This is
`higher than the recommended maximum concentration of
`45% by weight peroxide to assure suitable interactions with
`other materials. As discussed above, this peroxide concentra-
`tion or higher may not only cause spontaneous combustion
`and also may accelerate decomposition of peroxide or cause
`degradation of materials. Incompatible materials can in-
`clude painted surfaces and electronics. Peroxide condensa-
`tion also can decrease the useful life of chamber materials in
`
`particular, those used in flexible-walled isolators. Once the
`condensate is formed it will eventually have to be evaporated
`from the chamber as peroxide is removed at the end of a
`decontamination phase. The slow evaporation will cause the
`peroxide concentration in the liquid to reach even higher
`unsuitable concentrations regarding safety and degradation
`of materials.
`
`Decontamination reproducibilityis a further concern. When
`condensation occurs, the surfaces in the chamber may not get
`uniformly exposed, depending on how condensation occurs.
`Condensation can occur either in a drop wise or film form,
`depending on the nature ofthe contact surface. The determin-
`ing property is the surface tension of the solid surface. In
`general, film condensation occurs ifthe surface tension ofthe
`solid is at least 10 dynes/cm higher than the surface tension
`of the liquid condensing. The surface tension ofliquid perox-
`ide/water solutions range from 78 dynes/cm (pure water) to
`
`
`Temperaturel°Gl Maximum Hydrogen Peroxide Concentration
`
`(no condensation)
`(mg/L)
`
`0% Relative Humidity
`10% Relative Humidity
`
`Carrier Gas
`Carrier Gas
`
`
`
`
`
`
`0
`10
`20
`30
`40
`50
`60
`
`0.35
`0.77
`1.56
`3.01
`5.49
`9.60
`16.13
`
`0.28
`0.63
`1.28
`2.50
`4.60
`8.11
`13.68
`
`4. the chamber temperature“9
`
`Table B. Maximum peroxide vapor concentration at various
`temperatures.
`
`4
`
`PHARMACEUTICAL ENGINEERING JANUARY/FEBRUARY 2007
`
`©Copyright ISPE 2007
`
`Regeneron Exhibit 1051.004
`
`

`

`Decontamination Methods
`
`decomposed to water and oxygen in a destroyer and the water
`removed in a dryer. Drying the carrier gas stream is impor-
`tant as the water content in the carrier gas will affect the
`point at which condensation will occur as shown in Table B.
`For example, at 25°C, the maximum allowed concentration of
`peroxide vapor drops from 2.184 mg/liter to 1.805 mg/liter as
`the moisture content in the carrier gas goes from 0% RH up
`to 10% RH. This is a 17.4% drop in the maximum allowed
`peroxide concentration that may be introduced into the de-
`contamination chamber.
`
`Measuring and Controlling
`Peroxide Gas Concentration
`
`As shown above, Equations one through five may be used to
`calculate the maximum level of hydrogen peroxide that may
`be achieved in a chamber without causing condensation.
`Once the maximum peroxide vapor concentration is known,
`it is possible to develop an operating cycle that gives the
`maximum concentration of peroxide while preventing con-
`densation. The controlled variables for the cycle will include
`air flow rate, rate of injecting liquid peroxide into the flash
`vaporizer, concentration of the liquid to be flash vaporized,
`and the chamber temperature, volume, and humidity level.
`The peroxide and water concentrations during a cycle can be
`monitored using either infrared spectroscopy or electrochemi-
`cal methods.1°'11 It is desirable to run the peroxide concentra-
`tion as high as possible, but at the same time reducing the
`risk of producing condensation (typically targeting less than
`90% of the saturation level). It should be noted that these
`
`detector systems can only be used to monitor gas concentra-
`tions, where condensation of liquid will cause the sensor to
`fail. Overall, higher levels of peroxide vapor concentration
`will result in higher kill rates and therefore shorter cycle
`times, but it is recommended that this should be balanced by
`ensuring that condensation does not occur. Once the cycle is
`developed for a given volume and temperature, it may not be
`
`
`
`about 80 dynes/cm (pure peroxide). The surface tension for
`78% by weight peroxide liquid is about 78 dynes/cm. There-
`fore, drop-wise condensation will occur on solid surfaces with
`surface tensions less than about 88 dynes/cm when gas at
`85% by weight peroxide vapor is condensing. Recall that 85%
`by weight peroxide vapor condenses as 78% peroxide in the
`liquid. Polymer materials surface tensions typically range
`from 20 to 45 dynes/cm or lower. Therefore, drop wise conden-
`sation should occur on most polymer materials. Clean metal
`and glass surfaces typically have surface tensions that are
`higher than 200 dynes/cm. Contamination on a metal or glass
`surface may dramatically drop the surface tension allowing
`for drop wise condensation. Figure 8 shows how a contami-
`nant on a metal surface causes drop wise condensation. This
`will not allow the entire surface to be exposed to liquid
`resulting in a non-uniform surface exposure to peroxide.
`Even iffilm wise condensation occurs, there is a possibility of
`non-uniform liquid exposure on the surface due to developing
`liquid flow patterns on vertically sloped surfaces.
`A further complication associated with condensation of
`liquid is the additional time required to remove peroxide from
`the chamber at the end of an exposure phase. Gas can quickly
`be removed from the chamber by purging with an inert gas
`(such as air). Additional time is necessary to remove peroxide
`in the liquid form due to the time required to evaporate the
`liquid from all surfaces. If a material is permeable to liquid
`water or peroxide, additional time will be needed to remove
`any liquid that absorbed into the solid surface. Examples
`include porous materials and certain polymers, which are
`permeable to liquid water and/or peroxide.
`Finally, condensed peroxide at high concentration may
`have un-suitable (even violent) reactions with certain mate-
`
`rials in the decontamination chamber. Special safety precau-
`tions should be in place to handle any standing liquid hydro-
`gen peroxide condensate that can be violently reactive and
`will cause severe burns.
`
`Decomposition of Hydrogen Peroxide
`Hydrogen peroxide, especially in gaseous form or impure
`liquid solutions, is not a very stable compound. In particular,
`it spontaneously decomposes to form oxygen and water as
`shown below:
`
`H202 ® 1/2 02 + H20
`
`Therefore, the concentration of peroxide gas in the steriliza-
`tion chamber will steadily decrease over time, depending on
`the chamber area, material of construction, contents, etc. A
`simple procedure to maintain a constant peroxide concentra-
`tion involves continually circulating the gas in the steriliza-
`tion chamber through a system that regenerates fresh perox-
`ide vapor as shown in Figure 4. This design is successfully
`used in gaseous hydrogen peroxide decontamination sys-
`tems. Fresh peroxide gas produced from a flash vaporizer is
`introduced into the chamber as gas in the chamber is re-
`moved, thereby maintaining a consistent peroxide vapor
`concentration. Further, the removed peroxide gas can be
`
`
`
`
`
`
`y— Destroyer
`i
`
`Blower
`
`
`’m
`i} L1
`
`Decontamination L
`
`Area
`
`— D
`
`ryer
`
`
`FLU
`
`_+«l7.~
`
`Liquid
`
`&
`I“
`Hydrogen
`Flas
`‘
`\‘
`A—
`\J Vaporizer (NJ Peroxnde
`
`Figure 4. Typical Vaporized Hydrogen Peroxide (VHP)
`decontamination system. Vapor is produced by flash vaporization
`of liquid hydrogen peroxide and blown into a volume to be
`decontaminated. The vapor concentration is held constant by a
`constant flow of gas through a destroyer (e.g., x), air blower.
`
`©Copyright ISPE 2007
`
`JANUARY/FEBRUARY 2007
`
`PHARMACEUTICAL ENGINEERING
`
`Regeneron Exhibit 1051.005
`
`

`

`
`
`Decontamination Methods
`
`necessary to monitor peroxide and water concentration as
`long as the carrier gas flow and liquid peroxide injection rate
`are held constant.
`
`In conclusion, hydrogen peroxide in the vapor phase offers
`an effective, controllable, fast, and safe means of decontami-
`nating surfaces within a closed chamber of any size. Correct
`control of decontamination cycles is important to ensure that
`optimal and safe cycles are used for validated, repeatable
`applications.
`
`References
`
`1. Akers, J.E., Agalloco J.P., Kennedy C.M., “Experience in
`the Design and Use of Isolator Systems for Sterility
`Testing,” PDA JPharm Sci Technol., 1995, 49(8):140-4.
`
`2. Klapes, N.A., and D. Vesley, “Vapor-Phase Hydrogen
`Peroxide as a Surface Decontaminant and Sterilant,”
`Appl. Environ. Microbiol., 1990, 56: 508-506.
`
`8. Krause, J., G. McDonnell, and H. Riedesel,
`“Biodecontamination of Animal Rooms and Heat-Sensi-
`
`tive Equipment with Vaporized Hydrogen Peroxide,”
`Contemp. Topics Lab Anim Sci., 2001, 40: 18-21.
`
`4. McDonnell, G., and Russell, A.D., “Antiseptics and Disin-
`fectants: Activity, Action, and Resistance,” Clin. Microbiol.
`Rev., 1999, 12: 147-179.
`
`5. Schumb, W.C., Hydrogen Peroxide, monograph series,
`American Chemical Society, Reinhold Pub. Corp., 1955
`
`6. Block, SS, 1991. Peroxygen Compounds. p. 167-181. In
`S.S. Block (ed.). Disinfection, Sterilization, and Preserva-
`tion. 4th ed. Lea and Febiger, Philadelphia, PA.
`
`7. Davis, Jr., NS. and J. Keefe, Jr., J. Am. Rocket Society, p.
`68, March-April 1952 Buffalo.
`
`8. Scatchard, G., G. Kavanagh, and L. Ticknor, J., Am.
`Chem. Soc., 74, 8715, 1952.
`
`9. Pitzer, K. and L. Brewer, Thermodynamics, McGraw Hill,
`1961, Chapter 16 - 20.
`
`10. Day, R. and A. Underwood, QuantitativeAnalysis, McGraw
`Hill, 1961, chapter 14.
`
`11. Adams, D., G. Brown, C. Fritz, and T. Todd, “Calibration
`of a Near-Infrared (NIR) H202 Vapor Monitor,” Pharma-
`ceutical Engineering, Vol. 18, N0. 4, 1998, p. 66-82.
`
`12. Electrochemical Co., “Engineering Materials for Use with
`90% Hydrogen Peroxide,” Part 1, 1 December 1950.
`
`About the Authors
`Dr. Carl Hultman received his BS in chem-
`
`
`
`istry from the University of Wisconsin and
`his PhD in physical chemistry from the Penn-
`sylvania State University. He is currently a
`professor of chemistry at Gannon University
`in Erie, Pennsylvania. Dr. Hultman has pub-
`lished papers and received a patent for work
`in surface chemistry. His research interests
`include sublimation of solids, molten salt electrochemistry,
`and synthesis of nano-particle metal oxides. He is a member
`of the American Chemical Society. He can be contacted by
`phone at 1+814-825-5 144 or by e-mail at: hultman@
`gannon.edu.
`Gannon University, Department of Chemistry, University
`Square, Erie, Pennsylvania 16541.
`
`
`
`
`Aaron Hill received his BS and MS degrees
`in mechanical engineering from the Gannon
`University in Erie, Pennsylvania. He is cur-
`rently an engineering manager at Steris Cor-
`poration at their Erie, Pennsylvania facility.
`Hill has received four patents pertaining to
`vaporized hydrogen peroxide equipment. He
`was the project leader for several new vapor-
`ized hydrogen peroxide decontamination systems developed
`at Steris Corporation. He is a member of the American
`Society of Mechanical Engineers. He can be contacted by
`phone at: +1-814-870-8109 x8118 or by e-mail at:
`aaron_hill@steris.com.
`Steris Corporation, 2424 W. 28rd St., Erie, Pennsylvania
`16506.
`
`Dr. Gerald McDonnell has a BSc (Hons.) in
`
`
`
`medical laboratory sciences from the Univer-
`sity of Ulster and a PhD in microbial genetics
`from Trinity College Dublin. He is currently
`a Senior Director, Technical Affairs for Steris
`Corporation, based at their European head-
`quarters in Basingstoke, UK. Dr. McDonnell
`is widely published in the decontamination
`and sterilization area. His research interests include infec-
`
`tion prevention, decontamination microbiology, emerging
`pathogens, and the mode of action/resistance to biocides. Dr.
`McDonnell is the current editor of the Central Sterilisation
`
`Club (UK), and a member of the American Society of Micro-
`biology, Society for Applied Microbiology, Council of
`Healthcare Advisors, European Biological Safety Associa-
`tion, and AAMI. He can be contacted by phone at: +44-1256-
`866560 or by e-mail at: gerry_mcdonnell@steris.com.
`STERIS Limited, STERIS House Jays Close, Viables,
`Basingstoke, Hampshire RG22 4AX, UKB
`
`6
`
`PHARMACEUTICAL ENGINEERING JANUARY/FEBRUARY 2007
`
`©Copyright ISPE 2007
`
`Regeneron Exhibit 1051.006
`
`