Compatibility of Materials and Equipment with Chlorine- and Peracetic Acid-based Sporicidal Liquid Solutions


EPA/600/R-22/160 | Sept 2022
https://www.epa.gov/research

United States
Environmental Protectior
Agency

&EPA

Compatibility of Materials
and Equipment with
Chlorine- and Peracetic
Acid-based Sporicidal
Liquid Solutions

Office of Research and Development

Homeland Security Research Program

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oEPA

EPA 600/R-22/160

Compatibility of Materials and Equipment with Chlorine- and
Peracetic Acid-based Sporicidal Liquid Solutions

Joseph P. Wood, Principal Investigator:

U.S. Environmental Protection Agency (U.S. EPA)

Center for Environmental Solutions & Emergency Response (CESER)

Prepared by:

Stella McDonald
Timothy Chamberlain
Abderrahmane Touati, Ph.D.

Jacobs

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Disclaimer

The U.S. Environmental Protection Agency (EPA), through its Office of Research and
Development's Center for Environmental Solutions and Emergency Response
(ORD/CESER)/Homeland Security and Materials Management Division (HSMMD), directed and
managed this investigation through Contract No. 68HERC20D0018 with Jacobs Technology,
Inc. (Jacobs). This report has been peer and administratively reviewed and has been approved
for publication as an Environmental Protection Agency document. It does not necessarily reflect
the views of the Environmental Protection Agency. No official endorsement should be inferred.
This report includes photographs of commercially available products. The photographs are
included for purposes of illustration only and are not intended to imply that EPA approves or
endorses the product or its manufacturer. EPA does not endorse the purchase or sale of any
commercial products or services.

Questions concerning this document or its application should be addressed to the EPA Project
Lead listed below:

Joseph Wood

Office of Research and Development

U.S. Environmental Protection Agency (MD-E343-06)

109. T.W. Alexander Drive

Research Triangle Park, NC 27711

Phone: 919-541-5029

E-mail: wood.ioe@epa.gov

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Foreword

The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the
Nation's land, air, and water resources. Under a mandate of national environmental laws, the
Agency strives to formulate and implement actions leading to a compatible balance between
human activities and the ability of natural systems to support and nurture life. To meet this
mandate, EPA's research program is providing data and technical support for solving
environmental problems today and building a science knowledge base necessary to manage
our ecological resources wisely, understand how pollutants affect our health, and prevent or
reduce environmental risks in the future.

The Center for Environmental Solutions and Emergency Response (CESER) within the Office of
Research and Development (ORD) conducts applied, stakeholder-driven research and provides
responsive technical support to help solve the Nation's environmental challenges. The Center's
research focuses on innovative approaches to address environmental challenges associated
with the manufactured environment. The Center develops technologies and decision-support
tools to help safeguard public water systems and ground water, guide sustainable materials
management, remediate sites from traditional contamination sources and emerging
environmental stressors, and address potential threats from terrorism and natural disasters.
CESER collaborates with both public and private sector partners to foster technologies that
improve the effectiveness and reduce the cost of compliance, while anticipating emerging
problems. We provide technical support to EPA regions and programs, states, tribal nations,
and federal partners, and serve as the interagency liaison for EPA in homeland security
research and technology. The Center is a leader in providing scientific solutions to protect
human health and the environment.

This report assesses the impacts of four liquid sporicidal decontamination solutions (used for
Bacillus anthracis spore inactivation) on numerous materials and equipment.

Gregory Sayles, Director

Center for Environmental Solutions and Emergency Response

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Acknowledgements

The principal investigator from the U.S. Environmental Protection Agency (EPA), through its
Office of Research and Development's Center for Environmental Solutions and Emergency
Response (ORD/CESER)/Homeland Security and Materials Management Division (HSMMD),
directed this effort with the support of a project team from across EPA. The contributions of the
individuals listed below have been a valued asset throughout this effort.

EPA Project Team

Joseph Wood, CESER/HSMMD

Shannon Serre, OEM/CBRN CMAD

Ben Franco, On-Scene Coordinator, Region 4

Worth Calfee, CESER/HSMMD

Timothy Boe, CESER/HSMMD

Anne Mikelonis, CESER/HSMMD

Lukas Oudejans, CESER/HSMMD

Katherine Ratliff, CESER/HSMMD

EPA Quality Assurance

Ramona Sherman, CESER/HSMMD

Jacobs Technology. Inc.

Stella McDonald
Abderrahmane Touati
Timothy Chamberlain
Timothy McArthur
Stacy Cross

Authorship

The primary authors of this report are Stella McDonald, Abderrahmane Touati, Timothy
Chamberlain, and Joseph Wood.

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Table of Contents

Disclaimer	i

Table of Contents	iv

List of Figures	vi

List of Tables	viii

Acronyms and Abbreviations	ix

Executive Summary	x

Introduction	1

1.0 Project Description	1

2.0 Materials and Methods	2

2.1	Material Coupons Tested	2

2.2	Equipment	4

2.3	Sporicidal Liquid Solutions and Active Ingredient Analysis	5

2.4	Methods for immersing coupons in decontaminants	6

2.5	Rinsing methods	6

2.6	Equipment spraying methods	7

2.7	Photography Methods	9

2.8	Testing Frequency	11

2.9	Scoring Approach	11

2.10	Equipment test methods	11

2.10.1	Single-board computer testing	11

2.10.2	Circuit Breaker Testing	13

2.11	Wipe tests for residue	14

2.12	Sample Descriptions and Quantities	15

3.0 Results and Discussion	16

3.1 Visual Change Assessments	18

3.1.1	Metals	18

3.1.2	Plastics	26

3.1.3	Other Material (Laminates, Caulk)	31

3.1.4	Small Electrical Equipment	32

3.3	Equipment functionality results	36

3.3.1	Single-board computers	36

3.3.2	Circuit breakers	42

3.4	Assessment of Experimental Variables	43

3.4.1 Impact as a Function of Material Type	43

iv

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3.4.2	Impacts as a Function of Time	45

3.4.3	Impact by Decontaminant	45

3.4.4	Impact as Function of Rinsing	46

3.5 Wipe Tests for Residue	46

4.0	Quality Assurance	49

4.1	Quality Control	49

4.1.1 Data Quality Indicators	50

7.0 References	51

v

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List of Figures

Figure 2-2. Immersion test setup with coupons inside a polypropylene draining bin positioned

inside the immersion basin	6

Figure 2-3. Coupon rinsed with deionized water	7

Figure 2-4. (a) Spray chamber with equipment setup, (b) SLS spray application	8

Figure 2-5. Sprayed equipment positioned on the drying rack	8

Figure 2-6. (a) Switch box, (b) Single-board computer, and (c) Circuit breaker after application of

the spray procedure	9

Figure 2-7. Photo-documentation setup	10

Figure 2-8. Single-board computer docking station	12

Figure 2-9. Photograph of circuit breaker test rig	14

Figure 3-1. Bronze coupons at 2 months after (a) control, (b) dichlor unrinsed, (c) dichlor rinsed,
(d) DB unrinsed, (e) DB rinsed, (f) PAA unrinsed, (g) PAA rinsed, (h) PAB unrinsed,
and (i) PAB rinsed	19

Figure 3-2. Low carbon steel coupons at 2 months after (a) control, (b) dichlor unrinsed, (c)

dichlor rinsed, (d) DB unrinsed, (e) DB rinsed, (f) PAA unrinsed, (g) PAA rinsed, (h)
PAB unrinsed, and (i) PAB rinsed	20

Figure 3-3. Copper coupons at 2 months after (a) control, (b) dichlor unrinsed, (c) dichlor rinsed,
(d) DB unrinsed, (e) DB rinsed, (f) PAA unrinsed, (g) PAA rinsed, (h) PAB unrinsed,
and (i) PAB rinsed	21

Figure 3-4. Low carbon galvanized steel coupons at 2 months after (a) control, (b) dichlor

unrinsed, (c) dichlor rinsed, (d) DB unrinsed, (e) DB rinsed, (f) PAA unrinsed, (g)

PAA rinsed, (h) PAB unrinsed, and (i) PAB rinsed	22

Figure 3-5. Dichlor immersed materials of (a) unrinsed neoprene, (b) rinsed neoprene, (c)

unrinsed acrylic, and (d) rinsed acrylic	27

Figure 3-6. Diluted bleach immersed materials of (a) unrinsed neoprene, (b) rinsed neoprene, (c)

unrinsed acrylic, and (d) rinsed acrylic	28

Figure 3-7. PAA immersed materials of (a) unrinsed neoprene, (b) rinsed neoprene, (c) unrinsed

acrylic, and (d) rinsed acrylic	29

Figure 3-8. pH-Amended bleach immersed materials of (a) unrinsed neoprene, (b) rinsed

neoprene, (c) unrinsed acrylic, and (d) rinsed acrylic	31

Figure 3-9. Laminate plank coupons at 2 months after (a) dilute bleach unrinsed, (b) DB rinsed,

and (c) PAA unrinsed (d) PAA rinsed	32

Figure 3-10. Electrical switch box at 2 months after (a) control, (b) dichlor unrinsed, (c) DB

unrinsed, (d) PAA unrinsed, and (e) PAB unrinsed	33

vi

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Figure 3-11. Circuit breakers at 2 months after (a) control, (b) dichlor unrinsed, (c) DB unrinsed,

(d) PAA unrinsed, and (e) PAB unrinsed	34

Figure 3-12. single-board computer, USB port side at 2 months after (a) control, (b) dichlor

unrinsed, (c) dichlor rinsed, (d) DB unrinsed, (e) DB rinsed, (f) PAA unrinsed, (g)

PAA rinsed, (h) PAB unrinsed, and (i) PAB rinsed	36

Figure 3-13. Stressberry Test Results - Average Temperature Change (°C ± SD)	38

Figure 3-14. Sysbench average memory execution (s ± SD)	39

Figure 3-15. Sysbench average process execution (s ± SD)	40

Figure 3-16. Example of SD card at (a) baseline; (b) 1 day after exposure to dichlor and rinse
procedure, but prior to wiping SD card; and (c) 1 week post exposure and after
wiping of SD card	41

Figure 3-17. Circuit breaker average trip times (s ± SD)	42

Figure 3-18. Low carbon steel coupons exposed to dichlor, with and without rinse and wiping (a)

no rinse, no wipe; (b) no rinse, wiped; (c) rinsed, no wipe; and (d) rinsed, wiped	48

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List of Tables

Table 2-1. Material Coupons	3

Table 2-2. Equipment Tested	4

Table 2-3. Sporicidal Liquid Solutions Evaluated	5

Table 2-4. Score Guide for Visual Assessments	11

Table 2-5. Materials Included in the Residue Removal Tests	14

Table 3-1. Summary of Exposure Conditions	17

Table 3-2. Summary of Visual Impacts to Metals from Dichlor	23

Table 3-3. Summary of Visual Impacts to Metals from Diluted Bleach	24

Table 3-4. Summary of Visual Impacts to Metals from PAA	24

Table 3-5. Summary of Visual Impacts to Metals from pH-Amended Bleach	25

Table 3-6. Summary of Visual Impacts to Plastics from Dichlor	26

Table 3-7. Summary of Visual Impacts to Plastics from Diluted Bleach	28

Table 3-8. Summary of Visual Impacts to Plastics from PAA	29

Table 3-9. Summary of Visual Impacts to Plastics from pH-Amended Bleach	30

Table 3-10. Summary of Visual Changes to single-board computers	35

Table 3-15. Visual Impact as a Function of Material	44

Table 3-16. Impact as a Function of Time	45

Table 3-17. Impact as a Function of Sporicidal Liquid Solution	45

Table 3-18. Impact as a Function of Rinsing	46

Table 3-19. Scores Comparing Wiped and Unwiped Coupons	47

Table 4-1. Analysis Equipment Calibration Frequency	49

Table 4-2. DQIs for Critical Measurements	50

viii

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Acronyms and Abbreviations

A/V	Audio/visual

CESER	Center for Environmental Solutions and Emergency Response
COMMANDER Consequence Management and Decontamination Evaluation Room

DB	Diluted bleach

DHS	U.S. Department of Homeland Security

Dl	Deionized

DQI	Data quality indicator

EPA	U.S. Environmental Protection Agency

HDMI	High-definition multimedia interface

HDPE	High-density polyethylene

HP	hydrogen peroxide

hr	Hour(s)

L	Liter(s)

min	Minute(s)

ml_	Milliliter(s)

MOP	miscellaneous operating procedure

NIST	National Institute of Standards and Technology

ORD	Office of Research and Development, EPA

PAA	peracetic acid

PAB	pH-adjusted bleach

PVC	Polyvinyl chloride

ppm	parts per million

QA	quality assurance

QAPP	quality assurance project plan

QC	quality control

SD	standard deviation

SLS	Sporicidal liquid solution

USB	Universal Serial Bus

ix

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Executive Summary

In the event of a Bacillus anthracis spore release, there are several decontamination techniques
available that have proven effective in inactivating the spores on many types of materials from
laboratory testing and past field use. In addition to decontamination efficacy, there are other
criteria that may be used as the basis for the selection of a decontamination method, such as its
compatibility with materials. Some decontamination technologies may cause corrosion, loss of
functionality, leave a residue, and/or cause other damage to materials and equipment.

This study focused on the material compatibility of four liquid-based sporicidal decontaminant
solutions: pH-adjusted bleach (PAB), diluted bleach, peracetic acid (PAA), and dichloro-s-
triazinetrione (dichlor). These decontaminants have been shown to be effective in inactivating B.
anthracis or surrogate spores on numerous types of materials in laboratory testing. It should be
noted that disinfectants and sterilants products are regulated under the Federal Insecticide
Fungicide and Rodenticide Act. (While the PAA product we used for testing is registered with
EPA as a sterilant, and the bleach and dichlor products are registered with EPA for use against
several microorganisms, none of the decontaminants used in testing are registered specifically
for use against B. anthracis spores.) This investigation examined the impact of the four
decontaminants on small coupons of eight metals/alloys, twelve plastic materials, two laminate
materials, and silicone caulk. In addition, the study evaluated the compatibility with small
equipment, i.e., electrical switch boxes, circuit breakers, and single-board computers. The
coupons of the materials were exposed to the decontaminants via immersion, while the small
equipment was sprayed. After exposure to the decontaminant, the materials and equipment
were observed and photographed at time intervals of 1 day, 1 week, 4 weeks, 8 weeks, and 12
weeks, to document visual impacts over time such as corrosion and presence of residue. The
study also evaluated whether rinsing the material and equipment with water after exposure to
the decontaminant affected compatibility.

The small equipment was also tested for functionality: the single-board computers were tested
using diagnostic software tools that evaluated process and memory execution speeds, as well
as temperature increases when the processor was stressed. The circuit breakers were
evaluated for the time to trip when placed under a current load greater than their rating.

A scoring system was used to quantify any visible change to the coupons and equipment
following exposure to the decontaminants, with a score of 1 indicating no visual change
observed on the surface of the material, and a score of 5 indicating the entire surface was
impacted. The scoring method did not differentiate between superficial changes due to residue
or substantive damage from corrosion. For this reason, wipe tests were also performed on
select materials impacted by the decontaminant, to determine if the visible changes were
superficial and resolved by wiping, or if damage to the material was irreversible. Wipe testing
was performed at the end of the 12-week observation period.

The only metals that incurred visual impact to color, presumably because of oxidation/corrosion,
were the low carbon steel, copper, brass, and bronze. For these metals, rinsing with water
generally improved appearance, although for the coupons exposed to PAB, rinsing with water
appeared to have the least effect (suggesting rapid damage not reversible by rinsing). The PAA
decontaminant appeared to have the least visual impact of the four decontaminants, although
exposure to PAA left a considerable amount of residue on the galvanized steel. The electrical
switch boxes (made from galvanized steel) were only minimally impacted and limited to a white

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residue and a slight red discoloration on the cut edges, which was most prominent with those
exposed to dichlor.

The plastic material and laminate coupons, as well as the circuit breakers, were visually
impacted primarily with the presence of residue. In most cases, the residue was easily removed
with the water rinse procedure. The PAA decontaminant resulted in the least amount of residue
compared to the other decontaminants. The clear- and black-colored plastics allowed for better
photographic documentation of the residue, whereas the white plastics made discernment of the
presence of white residue more difficult.

For the single-board computers, the primary visual impact was deposition of moderate amounts
of white residue on the cases; none of the circuit boards had any residue. The exposed USB
and ethernet ports did show some slight discoloration for some of the units. None of the
exposed HDMI and A/V ports showed any discoloration (indicative of corrosion), although there
was some residue visible for the some of the unrinsed dichlor computers.

Based on the scoring methods, copper and the copper alloys (bronze and brass) had the
highest weighted scores, indicating these materials sustained the most impact. Low carbon
steel had the next highest weighted score. The plastic materials, laminates, and silicone caulk
generally all had relatively low weighted scores. The plastic with the highest weighted score was
neoprene.

Comparing the decontaminants using the scoring system, dichlor and PAB had the highest and
similarly weighted scores (indicating overall they had most impact on materials), followed by
diluted bleach and PAA. PAA had the lowest weighted score (i.e., the least visual impact of the
four decontaminants studied).

For the single-board computer functionality tests, the tests to evaluate any changes in processor
temperature increase were inconclusive. Similarly, the decontaminant and rinse condition did
not appear to have any substantial impact on memory execution times. A small increase in
average memory execution time was observed on Day-1 post-exposure for each
decontaminant, although in most instances, by 1-week post-exposure, the memory execution
times returned to baseline levels. In addition, nearly all the single-board computers exhibited
memory execution times at the 2-month mark that were lower than baseline execution times.

Except for the diluted bleach single-board computers, process execution time was relatively
consistent regardless of the decontaminant or rinse configuration. Unrinsed single-board
computers sprayed with diluted bleach showed a small increase in the average process
execution time (approximately 0.2 s) for the full 2-months post-exposure. Computers exposed to
the diluted bleach spray with rinse showed a substantial change in the average process
execution time at 1-day post-exposure.

During the functionality test period, a computer sprayed with diluted bleach (no rinse) and a
computer sprayed with diluted bleach (with rinse) were both unresponsive at 1-week post-
exposure. Their SD cards were removed, the contacts cleaned, and the cards reinserted into
their slots. This fix proved successful and functionality testing resumed. There were no
subsequent issues with the unrinsed unit. However, the rinsed, diluted bleach unit
malfunctioned again at month 1 and was not able to be recovered with troubleshooting efforts.
Another computer sprayed with PAB then rinsed malfunctioned at month 2.

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For the circuit breaker functionality test results, there were no failures, and in general, average
trip times were consistent across decontaminant, rinse condition, and post-exposure time. Trip
times for Day 1 tests increased from baseline conditions for the controls as well as for the
breakers exposed to dichlor and diluted bleach, although the increases were not substantial.
The trip times for both rinsed and unrinsed units exposed to PAB decreased over time.

xii

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Introduction

1.0 Project Description

In the event of a Bacillus anthracis (the causative agent of anthrax disease) incident, there are
several decontamination techniques available that have been proven effective in inactivating the
spores on many types of materials. In addition to decontamination efficacy, there are other
criteria that may be used as the basis for the selection of a decontamination method, such as its
cost, health and safety implications, availability, and compatibility with materials. The latter
criterion is the subject of this report. Some decontamination technologies may cause corrosion,
loss of functionality, leave a residue, and/or cause other damage to materials and equipment.
These issues may be inconsequential if the material is to be managed as waste. However,
certain items, such as sensitive electronics, mission critical equipment, and articles of personal
or societal significance, rarity, or cost may need to be decontaminated to allow for reuse. (U.S.
EPA, 2022).

Several studies have been conducted by EPA over the years to evaluate the material
compatibility of decontamination techniques that have been shown to be effective in inactivating
B. anthracis spores. These studies have primarily focused on gaseous or vapor-based chemical
decontamination methods such as chlorine dioxide gas, hydrogen peroxide vapor, methyl
bromide, methyl iodide, and ethylene oxide. The reader is referred to a few technical briefs that
have summarized all these studies (U.S. EPA, 2014; U.S. EPA, 2017A; U.S. EPA, 2022).

The study discussed in this report focused on the material compatibility of four liquid-based
sporicidal decontaminant technologies: pH-adjusted bleach (PAB), diluted bleach, peracetic acid
(PAA), and dichlor. These decontaminants have been shown to be effective in inactivating B.
anthracis spores on several types of materials (see for example, Wood and Adrion, 2019;

Calfee etal., 2012; Ryan etal., 2014; Wood etal., 2011 A; Wood etal., 2011B; U.S. EPA,
2011B; U.S. EPA, 2021; U.S. EPA, 2009; U.S. EPA, 2006). And while a few studies have been
conducted that incorporated some limited material compatibility evaluations of pH-adjusted
bleach or diluted bleach as part of their broader efforts (U.S. EPA, 2015; U.S. EPA; 2017C; U.S.
EPA, 2017D), the present study is the first of its kind to specifically examine material
compatibility of the four liquid decontaminants and compare their impacts under the same
conditions.

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2.0 Materials and Methods

The compatibility of several types of materials and equipment upon exposure to the four liquid
decontaminant chemicals was studied in this project. (A separate set of materials and
equipment was used for each decontaminant material compatibility evaluation.) Coupons of the
materials were exposed to the decontaminant via immersion, while the small equipment was
sprayed with the decontaminant. (Coupons were immersed as a worst-case approach for
application of the decontaminant.) After exposure to the decontaminant, the materials and
equipment were photographed at time intervals of 1 day, 1 week, 4 weeks, 8 weeks, and 12
weeks, to document visual impacts over time such as corrosion and presence of residue. The
small electrical equipment was also tested for functionality at the same time intervals post
exposure.

There were nine pieces of each material coupon and equipment used in the tests for each
decontaminant studied: one set of 3 replicates served as controls and was not exposed to the
decontaminant; another set of 3 replicates was exposed to the decontaminant and then rinsed
with water; and the third set of 3 replicates was exposed to the decontaminant, but not rinsed
with water afterward. (While we acknowledge that rinsing materials with water following
decontamination in a real scenario may not always be practical, the study included a rinsing
step to determine its effect, e.g., if it would improve compatibility.) Typically, one day was used
to expose all coupons to a particular decontaminant, and another day was used to expose the
small equipment to a particular decontaminant. However, there were instances when not all
materials were available on the day of exposure to a particular decontaminant, and so these
coupons were exposed on the day that the spray of small equipment was conducted. Further
details on all these methods are discussed below.

2.1 Material Coupons Tested

This investigation examined the impact of four decontaminants on small coupons of metals and
metal alloys, plastics, and other indoor building materials. Each set of material coupons was
immersed in the sporicidal liquid solution (SLS). The materials tested, vendor, and size of the
prepared coupons are listed in Table 2-1.

2

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Table 2-1. Material Coupons

Material

Material Matrix

Vendor

Material Description

1100 Aluminum

Metal

McMaster Carr

1 -in by 1 -in coupons, 0.063-in thick

101 Copper

Metal

McMaster Carr

1 -in by 1 -in coupons, 0.063-in thick

Low-carbon steel

Metal

McMaster Carr

1 -in by 1 -in coupons, 0.0625-in thick

316 Stainless steel

Metal

McMaster Carr

1 -in by 1 -in coupons, 0.063-in thick

260 Brass

Metal

McMaster Carr

1 -in by 1 -in coupons, 0.0625-in thick

220 Bronze

Metal

McMaster Carr

1 -in by 1 -in coupons, 0.0640-in thick

Tin

Metal

McMaster Carr

1 -in by 1 -in coupons, 0.0625-in thick

Zinc-Galvanized Low-Carbon Steel

Metal

McMaster Carr

1 -in by 1 -in coupons, 0.015-in thick

Acrylonitrile butadiene styrene

Plastic

McMaster Carr

1 -in by 1 -in coupons, 0.125-in thick

HDPE

Plastic

McMaster Carr

1 -in by 1 -in coupons, 0.125-in thick

PVC

Plastic

McMaster Carr

1 -in by 1 -in coupons, 0.125-in thick

Polyester film

Plastic

McMaster Carr

1 -in by 1 -in coupons, 0.250-in thick

Polypropylene

Plastic

McMaster Carr

1 -in by 1 -in coupons, 0.125-in thick

Polycarbonate

Plastic

McMaster Carr

1 -in by 1 -in coupons, 0.125-in thick

Acrylic (plexiglass)

Plastic

McMaster Carr

1 -in by 1 -in coupons, 0.125-in thick

Nylon

Plastic

McMaster Carr

1 -in by 1 -in coupons, 0.125-in thick

Polystyrene

Plastic

McMaster Carr

1 -in by 1 -in coupons, 0.125-in thick

Polyurethane

Polyurethane

McMaster Carr

1 -in by 1 -in coupons

Neoprene rubber

Neoprene

McMaster Carr

1 -in by 1 -in coupons

Butyl rubber

Rubber

McMaster Carr

1 -in by 1 -in coupons

Silicone caulk

Silicone

McMaster Carr

Bead placed on 1 -in by 1 -in coupons

Laminate sheet (used for
countertops)

Formica

Formica/ Home
Depot

1 -in by 1 -in coupons

Laminate flooring

Pergo

Pergo/ Home Depot

1 -in by 1 -in coupons

3

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2.2 Equipment

The physical and functional impact of the SLS on small electrical equipment was also studied.
The equipment tested in this investigation is listed in Table 2-2.

Table 2-2. Equipment Tested

Equipment

Description

Supplier

Circuit breaker

Siemens Load-Center Circuit
Breaker, 1 Pole, 10 amp

McMaster Carr

Single-board computer

Raspberry Pi Zero W, 512 Mb,
4GB EXT C8, SKU: PI4-4GB-
EXT128EW-C8-BLK

Cana Kit

Galvanized steel switch
box

2x3x1% inches

McMaster Carr

Prior to performing spray tests on the single-board computers, the project team selected which
ports to have open and exposed to the decontaminant and which to be sealed (to allow for
subsequent functionality testing). Ports that remained uncovered included the HDMI 1, A/V,
USB 2.0, USB 3.0, and Ethernet. The other ports were sealed with Kappler™ ChemTape® (p/n
99402YW) to prevent damage from contact with the SLS (See Figure 2-1). The sealed ports
included the power supply (USB-C), the screen display (HDMI 0) and one of the data transfer
connections (USB 3.0). A USB 2.0 port was also sealed due to its location beside the USB 3.0.

(a)

Figure 2-1. Single-board computer with ports sealed with ChemTape® in preparation for the
spray procedure

4

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2.3 Sporicidal Liquid Solutions and Active Ingredient Analysis

The four SLSs used in this study to assess impacts on materials are described below and
summarized in Table 2-3. The concentrations of the active ingredients used in the study for
each of the decontaminants were chosen based on previous studies demonstrating high
efficacy against Bacillus spores.

Table 2-3. Sporicidal Liquid Solutions Evaluated

Sporicidal Liquid
Solution (SLS)

Source

Active Ingredients

Chemical
Formula

pH amended bleach

Clorox germicidal concentrated
bleach and Fisher Scientific
glacial acetic acid1

Sodium Hypochlorite,
Hypochlorous Acid

NaOCI/ HCIO

Diluted bleach

Clorox germicidal concentrated
bleach

Sodium Hypochlorite

NaOCI

Dichlor

Brilliance for Spas

Sodium Dichloro-s-
triazinetrione or NaCbCsNsOs

C3H4Cl2N3Na05

Peracetic Acid

Minncare Cold Sterilant (RTU)

PAA, hydrogen peroxide

C2H403 /H2O2

1 glacial acetic acid was diluted to 5% for use in the preparation of PAB

Dichlor. Solutions of sodium dichloro-s-traizinetrione, better known as dichlor, were
prepared by dissolving pH stabilized chlorinating granules (Dichlor; Pool Solutions, Pool
Supply World, P/N PSW-CSC158-5; Durham, NC; 56 % available chlorine; EPA
Registration Number 1258-984) in deionized water to reach the target free available
chlorine (FAC) concentration of 20,000 ppm. Approximately 105 grams of the chlorinated
granules were dissolved into 3,000 ml_ of deionized water, and adjusted as needed, to
achieve the desired FAC concentration.

Diluted Bleach. A diluted bleach solution with a target FAC concentration of 20,000 ppm
was prepared by using Clorox® Concentrated Germicidal bleach (Ultra-Clorox® Germicidal
Bleach; Clorox® Professional Products Co.; Oakland, CA; EPA Registration Number 5813-
114) stock solution. A new container of Germicidal bleach, 7.55% hypochlorite, was
purchased before each test to ensure there was no degradation in the product. The diluted
bleach was initially prepared with a 1:4 ratio of germicidal bleach to water by diluting 4-L of
germicidal bleach in 12,000-ml of deionized water. The FAC was determined to be 18,209
ppm; therefore, an additional 900-ml of germicidal bleach was added for a 1:3.4 dilution.

pH Amended Bleach. The pH amended sodium hypochlorite solution (PAB) was prepared
using germicidal bleach (Clorox® Corp., Oakland, CA; approximately 8% hypochlorite; EPA
Registration Number 5813-114), water, and 5% acetic acid that was prepared from certified
glacial acetic acid. The target pH for each PAB solution was between 6.5-7.0 and a target
FAC concentration of 6,000 - 6,700 ppm. Adjustments were made, as needed, to achieve
the desired pH range and FAC concentration.

Peracetic acid. (Minncare® Cold Sterilant; Minntech Corp.; Minneapolis, MN; 5% PAA;
22% H2O2; EPA Registration Number 52252-4) Fresh stock solution of PAA was used to
prepare a solution of 0.5% PAA by diluting with deionized water. The prepared PAA
solution was analyzed using an analytical method applicable for PAA solutions containing
H2O2. The H2O2 content was first determined by an oxidation reduction titration with 0.1N
eerie sulfate reagent. After the endpoint of this titration was reached, an excess of

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potassium iodide was added to the sample. The hydroiodic acid formed in acidic media
reacted with the PAA to liberate iodine. A standard 0.0375N STS reagent was used to
titrate the liberated iodine. The endpoint of this titration was used to calculate the PAA
content (U.S. EPA, 2014 and Dixon, W.T.. 1966).

2.4 Methods for immersing coupons in decontaminants

For each test condition, six replicate test coupons were immersed in a polypropylene basin
(Cambro 1/2 Food Pan 4" Deep, UPC Code: 10099511343765) containing 650 mL of SLS
(Figure 2-2). A station for each material was staged with the polypropylene basin and two small
draining bins. One bin was designated for immersing the coupons in the SLS and removing
them. The other bin was designated as the "clean bin" where coupons were transferred after the
rinse procedure. For each material, a total of 6 coupons were immersed; 3 would be rinsed after
the 60-min exposure and 3 would remain unrinsed. A team of 2 technicians worked in unison to
immerse and rinse coupons to ensure precise immersion and rinse times.

Figure 2-2. Immersion test setup with coupons inside a polypropylene draining bin

positioned inside the immersion basin

2.5 Rinsing methods

Following immersion of one set of coupon materials in SLS for 60 min, the team of technicians
removed the draining bin from the SLS. in concert, the team applied the rinse procedure one at
a time to 3 of the 6 drained coupons, placing the rinsed coupons in the "clean" bin while the
unrinsed coupons remained in the original draining bin. The rinse was applied with the coupon
positioned directly over the immersion basin so that the rinse run-off would collect with the SLS
waste.

The rinse procedure was as follows:

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1. Using a fresh pair of individually wrapped forceps, a coupon was removed from the
draining basin,

2. the frontside was rinsed with deionized water for 5 seconds using a squeeze bottle,

3. the coupon was flipped and the backside rinsed for 5 seconds,

4. the position of the forceps was moved and the backside was rinsed for 5 seconds again,
and

5. the coupon was turned over to the frontside and rinsed for 5 seconds again.

Coupons were individually and gently rinsed for a 5 second spray time, using 2 sprays per side,
for a total spray rinse time of at least 20 seconds. With the rinse procedure completed, the
coupon was placed in the "clean" bin to dry. The rinse procedure was performed on a total of 3
coupons per set of 6. The draining bin with the triplicate set of unrinsed coupons and the clean
bin with triplicate rinsed coupons were both placed on absorbent material to dry overnight.
Figure 2-3 shows a coupon being rinsed with deionized water.

Figure 2-3. Coupon rinsed with deionized water

2.6 Equipment spraying methods

The small equipment was exposed to the SLS using spray methods customized specifically for
each equipment type. The SLSs were spray-applied in a spray chamber using an industrial
sprayer bottle (32-oz plastic spray bottle; Lowes Inc, Mooresville, NC; Model No. S-7273 or
equivalent). The spray bottle was equipped with a trigger sprayer and adjustable spray pattern
(from mist to steady stream) and was recommended by the manufacturer for general household
cleaning purposes, including application of concentrated formulas.

The spray procedure was performed on single-board computers, circuit breakers, and switch
boxes. A total of 6 of each item were included in each SLS exposure: 6 were sprayed with the
SLS, 3 were rinsed with deionized water, and 3 remained unrinsed. In preparation for the spray
procedure, each item was individually placed inside a draining bin (Section 2.5) to contain any
overspray generated while applying the spray procedure. The chamber's exhaust system was
used to vent chemical vapors from the chamber.

Flow rate checks were performed on each spray bottle before SLS application. The spray
nozzle was adjusted as necessary to achieve a targeted 2.3 mL/spray. Figure 2-4 shows the
spray chamber with equipment prepared for the spray application.

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Figure 2-4. (a) Spray chamber with equipment setup, (b) SLS spray application

Switch boxes were sprayed three times with the SLS. The application of the initial spray initiated
a 60-minute contact period. After the initial spray, the second spray was applied at 20 minutes
and the third spray was applied at 40 minutes, to maintain a wet surface over the 60-min period.
Upon completion of the 60-min contact time, the rinse procedure was performed on 3 units by
applying four sprays of deionized water. Each unit, rinsed or unrinsed, was transferred to a
polypropylene rack and then to a drying chamber and allowed to dry overnight.

After completing the 18-hour drying phase, the equipment was transferred for storage and
photography. The label contained the material type, SLS, test date, and rinse condition (rinsed,
or unrinsed).

Figure 2-5 shows the exposed equipment positioned on the drying racks for the drying step.

Figure 2-5. Sprayed equipment positioned on the drying rack

Single-board computers were sprayed a total of five times with the SLS. The first spray was
applied with the unit positioned bottom side up. The unit was then turned right side up and each

8

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of the four sides was sprayed once. After completing the spray procedure, the unit was allowed
to dry for 60 minutes. Excess solution was drained from the top surface before transferring the
unrinsed units to the drying tray. Units designated for the rinse procedure were drained of
excess SLS and the spray procedure repeated with deionized water. Upon completion of the
rinse procedure, the units were transferred to the equipment drying rack.

Circuit breakers were sprayed once with SLS and allowed to dry for 60 minutes. Excess solution
was drained from the top surface before transferring the unrinsed equipment to the drying tray.
Equipment designated for the rinse procedure was drained of excess SLS, then sprayed twice
with deionized water. After completing the rinse procedure, the units were transferred to the
equipment drying rack.

Figure 2-6 shows the materials that received spray application of the SLS (switch box, single-
board computer, and circuit breaker).

Figure 2-6. (a) Switch box, (b) Single-board computer, arid (c) Circuit breaker after

application of the spray procedure

All supplies used to prepare, measure, dispense, and contain SLS were constructed of
chemically compatible materials.

2.7 Photography Methods

Impacts to material coupons and the small equipment were documented via photography using
a photo light box setup. The light box was placed on a mounted stand and the camera was set
to a fixed position of approximately 8-inches above the black felt background surface. A black
display board was cut to fit over the camera setup to stop the reflection of the white ceiling tiles.
To generate consistent photos for accurate comparisons, the photo light box setup was used to
document all materials from Month 1 until completion.

Initially, photographic documentation was captured using an iPhone 11 Pro or Android S22 and
a phone halo light stand using a pink background. The resulting photographs were inconsistent
in terms of the lighting and background. We then switched to a digital camera (Canon EOS
Rebel XSI DSLR), which provided more consistent photographic results. The same camera was
used to document all material results.

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The settings for the camera were as follows:

•	Photo setting: Manual

•	ISO speed: ISO 400

•	Shutter speed: 1/60

•	Aperture: F5.6

Figure 2-7 shows the lightbox and camera used for photo-documentation.

Figure 2-7. Photo-documentation setup

Metal and plastic material coupons were stored and photographed inside petri dishes. To photo-
document the coupons, the petri dish with coupons was transferred to the lightbox and the petri
dish lid was removed and placed beside the base with the label visible. The coupons were
never removed from the base of the petri dish or handled in any way. After photography was
completed, the lid was replaced, and the Petri dish placed in a rack and stored in an
environmentally controlled laboratory.

Four photos were taken of each switch box. Each single-board computer was unplugged and
disassembled, with the micro-USB being taken out before each set of photos. Once the
computers were taken apart, a photo of both sides and all the ports on the board were
documented as well as the micro-USB. After being photographed, the computers were each
reassembled and plugged back into the appropriate docking station described in Section 2.10.2.
Photos of the attached label along with both the front and back sides of the circuit breakers
were taken.

10

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2.8 Testing Frequency

Temporal evaluations were performed to assess the impact of time on the functionality of
equipment and the appearance of the material coupons. Functionality testing and photo-
documentation was performed and documented at the following time intervals:

• 1-day

• 1-week

• 4-weeks

• 8-weeks

• 12-weeks

The required assessments were performed within ±5% of the scheduled times.

2.9 Scoring Approach

A scoring system was developed to quantify the visible change to the coupons and equipment.
A scale of 1-5 was used where 1 indicates no visual change (compared to controls) observed on
the surface of the material, and 5 indicates the entire surface was impacted by the test
condition. This system does not differentiate between superficial changes due to residue or
substantive damage from corrosion. Table 2-4 details the score guide for the visual
assessments.

Table 2-4. Score Guide for Visual Assessments

Score

Percentage of surface visibly changed
(x)

0% < x < 25%

25% < x < 50%

50% < x < 75%

75%
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and aluminum case body, and was powered by the manufacturer-provided AC/DC adapter. The
single-board computer assembly consisted of the following:

• Single-board computer 4 Model B with 1 5GHz 64-bit quad core ARMvS CPU

• SD card: Samsung EVO 128GB High Speed MicroSD preloaded with NOOBS

• CanaKit 3.5A USB-C Power Supply

• Self-cooling (direct contact to CPU) aluminum case

A single USB peripheral cable (A/B) was connected to one of the four Port HVM Switch Inputs
and one HDMI cable was connected to the associated HDMI input on the 4 Port KVM Switch.
This was repeated for 4 assemblies on a single 4 Port KVM Switch. The docking station
consisted of one (1) TESmart 8 Port HDMI KVM Switch (Product HKS1601A10) and seven (7)
PWAY(GreatHTek) 4 Port HDMI KVM Switches (Product PW-SH0401B) as shown in Figure 2-
8.

Figure 2-8. Single-board computer docking station

Each 4 Port KVM Switch's output (HDMI and USB) was connected to an input on the 8 Port
KVM Switch. The output from the 8 Port KVM Switch was connected to a keyboard/mouse
combo unit and an HDMI monitor. This system supported up to 32 connected single-board
computer units and allowed for one keyboard/mouse and one HDMI monitor to be used to
control all the single-board computers associated with this project. To select an individual unit,
the operator only had to make the appropriate selections with physical buttons on the KVM
Switches (both 4 Port and 8 Port).

The system was preloaded with NOOBS software, which is an easy-to-use install for Raspbian
and other Linux distributions commonly installed on single-board computers. Raspbian was
installed from the pre-loaded NOOBS SD for this project. The two software packages below
were chosen to monitor system performance before and after exposure to the decontaminants.

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Stressberry is a free software tool (downloaded from Github.com) that stresses the processor by
running it at high frequency to increase the temperature of the CPU. The temperature and
frequency are monitored during the test and recorded in a log file which is used to generate a
graph of temperature and frequency over the duration of the test. It is generally used to
compare different cooling techniques of the CPU, such as passive vs active cooling. If the
cooling hardware is the same (for this project, just the passive case cooling with direct metal
contact to the CPU), then any variation in the temperature (specifically the change in
temperature since the lab temperature may vary as well) can possibly be attributed to impact on
CPU performance. To determine the average change in temperature, the pre-stress test
temperature was subtracted from the post-stress test temperature for each individual unit. Then
the differences for each triplicate set were averaged.

Sysbench was also used and is a benchmark tool commonly used to test database servers but
can be run on individual machines. A total of two Sysbench tests were conducted for this
investigation: process execution and memory execution tests. For the process execution test,
the CPU runs a sequence of logic tests on a data set and records the execution time for each
request. This same test is performed at every evaluation to determine if the processor
completes the instructions at the same speed. Similarly, the memory test simply copies a large
data set (2GB) from one memory location to another. This determines the read and write speed
of the memory and records the execution time per 1MB block of data. The purpose of this test
is to identify pre- and post-exposure variations in execution time.

2.10.2 Circuit Breaker Testing

A custom-designed and built circuit breaker test rig consisted of an electrical panel (box)
containing a Ground Fault Circuit Interrupter (GFCI), a contactor (relay), a power indicator light,
and associated terminals and wiring. An electrical panel housed the mounting rail for the
breakers and a safety interlock switch. The entire configuration was controlled by a spring-
loaded foot switch. Power could only be supplied when the switch was closed.

A 12-amp current load was generated using a heat gun (Master Flow model AH751) and the
primary amperage was measured with a current clamp (Model i200; Fluke Corporation, Everett,
WA). A secondary current probe was used for quality control (Onset, CTV-B). The probes in the
main panel were approximately 2 inches apart. A probe was connected to each Fluke 87 V
multimeter. Voltage measurements were conducted using a Kill-A-Watt EZ P3 power monitor on
a power strip that was plugged into the same outlet circuit as the testing system.

The breaker was installed in the test rig by placing it into the breaker panel. The foot switch
started simultaneously with a NIST traceable timer. After 30 seconds, the current applied to the
breaker was recorded. The time required for the breaker to "trip" was noted on the data sheet.
Power was removed from the breaker and the foot switch released. Once the breaker was reset,
the heat gun was placed in the "cool" position. After cool-down, the power was removed, the
breaker was uninstalled, and the next breaker in the series was installed in the breaker panel.
This process was repeated until all breakers were tested.

At the start of each test day, line voltage was measured with and without a load. At the end of
each day, the line voltage was remeasured with and without a load. While performing the first
breaker test, an additional current reading was taken at the 30 second mark as an independent
Daily QC Check on the multimeter.

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Figure 2-9. Photograph of circuit breaker test rig

2.11 Wipe tests for residue

Wipe tests were performed on select materials impacted by the deconta mi riant exposure to
determine if the visible changes were superficial and resolved by wiping, or if damage to the
material was irreversible. Table 2-5 lists the materials included in the wipe tests.

Table 2-5. Materials Included in the Residue Removal Tests

Metals

Plastics and other Materials

Copper

Laminate sheet

Aluminum

PVC

Stainless Steel

acrylic

Low carbon steel

butyl rubber

Wipe testing was performed following the 12-week photographic documentation. Photographs of
the material before and after wiping were assessed for substantial changes.

To execute the procedure, a photograph was taken of each 1"x1" coupon. The coupon was
picked up with forceps and wiped with an anti-static Kimwipe, twice in one direction, then turning
the coupon 90 degrees and wiping twice in that direction. A Kimwipe was used to reduce
depositing lint onto the coupons. Immediately after this wiping procedure, another picture was
taken using the same method and camera setting as before. Wiping was conducted for both

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rinsed and non-rinsed coupons for materials selected for wiping. No chemical analyses of the
residue was conducted.

2.12 Sample Descriptions and Quantities

Control samples were a set of three replicate material coupons or equipment that were not
exposed to any decontaminant. These coupons were used to display the effect of natural
degradation over time that occurred to each material without exposure to the SLS.

Test coupons and equipment were photographed and documented before exposure to the SLS
to establish a baseline. The baseline documentation was used to compare how much
degradation occurred over the 12-week period.

The test samples were a set of three replicate material coupons that were exposed to the SLS.
These samples showed the effect of the applied decontaminant to rinsed and unrinsed materials
over the 12-week period, as described above.

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3.0 Results and Discussion

The active ingredient concentrations of each SLS for each exposure event are summarized in
Table 3-1. The FAC concentrations for the batches of diluted bleach and dichlor were within 5%
of the targeted 20,000 ppm. The FAC concentrations for prepared batches of PAB were 6,600
mg\L and 6,409 ppm. The concentrations of the two PAA solutions were 0.4% PAA and 0.5%
PAA.

Laminate materials (sheet and flooring) were not included in either of the initial dichlor or diluted
bleach immersion events. These materials were unavailable at the time and therefore
processed in parallel with the dichlor and diluted bleach equipment spray tests.

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Table 3-1. Summary of Exposure Conditions

Test
ID

Sporicidal
Liquid Solution

FAC (ppm)
in solution

Measured PAA
(%) in solution

Measured HP
(%) in solution

Measured pH
of solution

Comments

Immersion Tests

dichlor

20,320

6.92

Immersion test for all material coupons
except laminate sheet, laminate flooring,
and silicone caulk.

diluted bleach

20,030

12.02

Immersion test for all material coupons
except laminate sheet, laminate flooring,
and silicone caulk.

PAA

0.5

2.44

Immersion test for all material coupons
except silicone caulk.

PAB

6,600

6.84

Immersion tests for all material coupons
except silicone caulk.

Spray Tests

dichlor

19,136

6.43

Spray tests for small equipment; immersion
test for laminated materials and silicone.

diluted bleach

20,608

11.35

Spray tests for small equipment; immersion
tests for laminated materials and silicone.

PAA

0.4

2.48

Spray tests for small equipment; immersion
tests for silicone material only.

PAB

6,409

7.06

Spray tests for small equipment; immersion
tests for silicone material only.

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3.1 Visual Change Assessments

Information provided in this section reflects observations and photo-documentation taken at the
1-week and 2-month durations. The appearance of the materials remained relatively unchanged
between the 1-week and 2-month durations (see Section 3.4.2) and therefore, the information
provided is applicable for both time points.

The term "residue" is used to denote the presence of a solid material or particulate substance
on the surface of the material. Chemically analyzing the residue was outside the scope of work
for this investigation.

3.1.1 Metals

Overall, the only metals or alloys that incurred visual damage/impact (to color, presumably as a
result of oxidation/corrosion) were the low carbon steel, copper, brass, and bronze. For these
metallic coupons, rinsing after the 60-minute exposure generally improved appearance,
although for the coupons exposed to PAB, rinsing appeared to have the least effect (suggesting
rapid damage that was not reversible by rinsing with water). The PAA decontaminant appeared
to have the least visual impact of the four SLSs on the low carbon steel, copper, brass, and
bronze, although exposure to the PAA solution left a considerable amount of residue on the
galvanized steel. Refer to figures below for photographs taken at 2 months post exposure as
examples of the impact to some of the metals. Further details on the impacts of each of the four
SLSs are summarized below.

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Figure 3-1. Bronze coupons at 2 months after (a) control, (b) dichlor unrinsed, (c) dichlor
rinsed, (d) DB unrinsed, (e) DB rinsed, (f) PAA unrinsed, (g) PAA rinsed, (h) PAB unrinsed,

and (i) PAB rinsed

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Figure 3-2. Low carbon steel coupons at 2 months after (a) control, (b) dichlor unrinsed, (c)
dichlor rinsed, (d) DB unrinsed, (e) DB rinsed, (f) PAA unrinsed, (g) PAA rinsed, (h) PAB

unrinsed, and (i) PAB rinsed

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Figure 3-3. Copper coupons at 2 months after (a) control, (b) dichlor unrinsed, (c) dichlor
rinsed, (d) DB unrinsed, (e) DB rinsed, (f) PAA unrinsed, (g) PAA rinsed, (h) PAB unrinsed,

and (i) PAB rinsed

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Figure 3-4. Low carbon galvanized steel coupons at 2 months after (a) control, (b) dichlor
unrinsed, (c) dichlor rinsed, (d) DB unrinsed, (e) DB rinsed, (f) PAA unrinsed, (g) PAA
rinsed, (h) PAB unrinsed, and (i) PAB rinsed

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Dichlor: The dichlor treatment resulted in damage to the surfaces of copper, bronze, brass, and
low carbon steel, and completely changed their appearances. Applying the rinse step after
immersion reduced the severity of the impact, but not enough to maintain the original
appearance of the material. Table 3-2 summarizes the visual changes (as compared to controls)
resulting from dichlor immersion on the metals/metal alloy coupons.

Table 3-2. Summary of Visual Impacts to Metals from Dichlor

Material

Visual Change for Unrinsed and Rinsed Coupons

Unrinsed

Rinsed

Aluminum

A thin border of white residue formed
around edges and several spots on the
surface

No visual change

Brass

Significant changes in surface color
and texture

Changes in color and texture; similar area
affected as unrinsed material with less
severity

Bronze

Significant changes in surface color
and texture (patina; turquoise)

Changes in color and texture resemble
unrinsed materials with less severity

Copper

Changes in color and texture over the
entire surface of the coupons

Changes in color and texture comparable
to the unrinsed coupons

Low-carbon
steel

Changes in color (rust) and texture
(over majority of surface)

Changes in color and texture resemble
unrinsed material with less severity

Stainless steel

Few spots of white residue

No visible change

Tin

Significant amount of white residue

Border of white residue formed around
edges of the coupon

Zinc-Galvanized

Low-Carbon

Steel

Few small spots of white residue

No visible change

Diluted bleach: After immersion in diluted bleach, deposits of white residue were observed on
the surfaces of tin, aluminum, and zinc-galvanized steel coupons. In each case, the residue
accumulation was low. Rinsing the surfaces eliminated the residue only moderately on the tin
and zinc-galvanized steel. Diluted bleach immersion resulted in significant changes in the color
and texture of brass, bronze, copper, and low-carbon steel. The appearance of unrinsed
coupons of these materials was completely altered compared to controls. Although the damage
was substantial for unrinsed materials, applying the rinse step after immersion appeared to
mitigate the damage in some cases. In the case of stainless steel, there were no changes in the
appearance of the coupons. The appearance of rinsed materials remained comparable to
baseline observations with small areas of discoloration. Table 3-3 summarizes the visual
changes resulting from diluted bleach immersion on the metals.

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Table 3-3. Summary of Visual Impacts to Metals from Diluted Bleach

Material

Visual Change for Unrinsed and Rinsed Coupons

Unrinsed

Rinsed

1100 Aluminum

Significant amount of white
residue

Some white residue remaining

Brass

Change in color and texture

Slight residue and
discoloration on surface

Bronze

Significant change in surface
color (green) and texture

Moderate discoloration and
darkening

Copper

Changes in color and texture

Mild to moderate discoloration

Low-carbon steel

Significant changes in color
(rust) on surface

Mild red/orange discoloration
on corners and edges

Stainless steel

Small amount white residue

No visible changes

Tin

Slight white residue

Zinc-Galvanized Low-Carbon Steel

White residue

PA A: A few small areas of white residue were observed on the aluminum coupons 2-months
after immersion in PAA solution. The residue was not present on the rinsed coupons. Low-
carbon steel was minimally impacted, with a few small, discolored areas on the surface of the
coupons. Applying the rinse step prevented these changes in the material. Brass, bronze,
copper, and zinc-galvanized steel responded to the PAA treatment with significant changes in
color and texture. These changes were substantial and persisted through the application of the
rinse step. A significant accumulation of a white substance was observed on the surface of zinc-
galvanized steel. The appearance of the substance differed significantly from the white crystal
powder deposits from chlorine based SLS. Table 3-4 summarizes the visual changes resulting
from PAA immersion on impacted metals.

Table 3-4. Summary of Visual Impacts to Metals from PAA

Material1

Visual Change

Unrinsed

Rinsed

Aluminum

Slight residue observed at 2-months

No visible changes

Brass

Changes in surface color (white, black) and
texture

Changes in color and texture
resemble unrinsed material with less
severity

Bronze

Significant change in color and texture

Change in color (dull color)

Copper

Changes in color (brown, green, and red)

Changes in color not related to
residue (dull, white haze)

Low-carbon steel

Few discolored spots (red)

Few discolored spots

Zinc-Galvanized
Low-Carbon Steel

Significant change in surface color and texture
due to white discoloration covering the surface

Significant change in color and
texture like the unrinsed coupons

1Tin and stainless steel did not show visible changes at any time during the 1 -week or 2-month observation
periods for either rinse condition.

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PAB: The pH-Amended bleach immersion resulted in deposits of white surface residue on
stainless-steel, tin, and zinc-galvanized steel coupons. Applying the rinse step prevented the
occurrence of white reside for stainless steel and reduced the severity of the residue buildup for
the other materials. Changes in the surface texture and color of aluminum, brass, bronze,
copper, and low-carbon steel coupons were observed. The impact was severe and significantly
altered the appearance of these coupons. Applying the rinse step, in most cases, would reduce
the impact of PAB, but not enough to maintain the appearance of the material. Table 3-5
summarizes the physical change from pH-amended bleach for impacted metals.

Table 3-5. Summary of Visual Impacts to Metals from pH-Amended Bleach

Material

Visual Change

Unrinsed

Rinsed

Aluminum

Changes in surface texture, with
spotting of residue

Similar changes in color and texture resemble
unrinsed material with less severity

Brass

Changes in surface texture and color
(green)

Similar changes as unrinsed materials. It
appears as if excess residue was removed,
revealing damage to the surface of material

Bronze

Changes in surface texture and color

Similar changes in color and texture resemble
unrinsed material with less severity

Copper

Changes in surface texture and color

Changes in surface texture and color
comparable to the unrinsed material

Low-carbon steel

Changes in texture and color (red)

Similar changes in color and texture resemble
unrinsed material with less severity

Stainless steel

Few spots/deposits of white residue

No visible changes

Tin

White surface residue

White surface residue present but not extensive
as the unrinsed material

Zinc-Galvanized

Low-Carbon

Steel

Thin border of white residue around
edges of coupons

No visible changes

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3.1.2 Plastics

Overall, the plastic material coupons were impacted by the SLS primarily with the presence of
residue. In most cases, the residue was easily removed with the rinse procedure. The PAA
decontaminant resulted in the least amount of residue compared to the other SLSs. The clear
(e.g., acrylic, polycarbonate) and black-colored plastics (neoprene, ABS) allowed for better
photographic documentation of the residue, whereas the white plastics such as polypropylene
and polystyrene made discernment of the presence of white residue more difficult.

Dichlor: The plastic materials that exhibited visual change after immersion in dichlor are
documented in Table 3-6. In most cases, visual changes were superficial white residue that was
resolved by applying the rinse procedure. Acrylic was the only material that had residual white
residue after applying the rinse procedure. Plastics that had no apparent visual changes (rinsed
or unrinsed) included polyester film and polypropylene. Example photographs of some of the
more relatively impacted plastics are shown in Figure 3-5.

Table 3-6. Summary of Visual Impacts to Plastics from Dichlor

Material

Visual Change for Unrinsed and Rinsed Coupons

Unrinsed

Rinsed

Acrylonitrile
butadiene styrene

Thin border of white residue around edges; few large to
medium sized patches of white residue

No visible changes

Acrylic (plexiglass)

Thick border of white residue around the edges with a few
patches in the center

Trace amounts of
white residue

Butyl rubber

Few patches of white residue

No visible changes

HDPE

White residue

No visible changes

Nylon

White residue around border and few spots

No visible changes

Neoprene

Few patches of white residue

No visible changes

Polycarbonate

Slight amount of white residue

No visible changes

Polystyrene

Small amount of white residue

No visible changes

Polyurethane

Few small spots of white surface residue

No visible changes

PVC

Small to med spots of white surface residue

No visible changes

Plastics that showed no visible change include polyester film and polypropylene.

-------
(a)

(b)

(c)

Figure 3-5. Dichlor immersed materials of (a) uririnsed neoprene, (b) rinsed neoprene, (c)

unrinsed acrylic, and (d) rinsed acrylic

-------
Diluted bleach; In most cases, the visual changes resulting from immersion in diluted bleach
were mild deposits of a superficial white residue. Heavy deposits of white residue were
observed on plexiglass. Rinsed plastics showed no sign of visible change from residue.
Materials that were not impacted by immersing in diluted bleach include butyl rubber,
polycarbonate, polystyrene, and polyurethane.

Table 3-7. Summary of Visual Impacts to Plastics from Diluted Bleach

Material

Visual Change for Unrinsed and Rinsed Coupons

Unrinsed

Rinsed

Acrylonitrile butadiene styrene

Light white surface residue

No visible change

Acrylic (plexiglass)

Severe in color and texture

No visible change

Nylon

Light white surface residue

No visible change

Neoprene

Light surface residue

No visible change

Polyester film

Slight white surface residue

No visible change

Polypropylene

Slight white residue

No visible change

PVC Plastic

Slight white residue

No visible change

Materials with no visible change included butyl rubber, polycarbonate, polystyrene, and
polyurethane.

Figure 3-6. Diluted bleach immersed materials of (a) unrinsed neoprene, (b) rinsed
neoprene, (c) unrinsed acrylic, and (d) rinsed acrylic

-------
PA A: Materials that showed visual changes after immersing in PAA include acrylic and
neoprene. A few areas of superficial surface residue were observed on acrylic. A clear, dull
residue was observed on the surface of neoprene. Materials rinsed with deionized water
maintained their pre-exposure appearance with no visual changes.

Materials not impacted by immersion in PAA include acrylonitrile butadiene styrene, butyl
rubber, HDPE plastic, nylon, polycarbonate, polyester film, polypropylene, polystyrene,
polyurethane, and PVC plastic.

Table 3-8. Summary of Visual Impacts to Plastics from PAA

Material

Visual Change for Unrinsed and Rinsed Coupons

Unrinsed

Rinsed

Acrylic (plexiglass)

Few drops of white surface residue

No visible change

Neoprene

Clear superficial residue

No visible change

All other plastic materials showed minimal residue.

Figure 3-7. PAA immersed materials of (a) unrinsed neoprene, (b) rinsed neoprene, (c)

unrinsed acrylic, and (d) rinsed acrylic

-------
PAB: Unrinsed neoprene had clear residue that appeared to be superficial. A substantial
amount of white residue remained on the surface of the acrylic material. Applying the rinse
procedure was moderately effective at preventing the residue. In each of the remaining cases,
rinsing PAB from the material surface proved effective for preventing residue.

Plastic materials not impacted by pH-amended bleach immersion were butyl rubber, HDPE
plastic, polyester film, and polypropylene.

Table 3-9. Summary of Visual Impacts to Plastics from pH-Amended Bleach

Material

Visual Change for Unrinsed and Rinsed Coupons

Unrinsed

Rinsed

Acrylonitrile
butadiene styrene

White residue formed thin border around edges, several spots

No visible change

Acrylic (plexiglass)

Significant buildup of white residue around edges

Trace amounts of
white residue

Nylon

Unrinsed - no visible change, rinsed - moderate border of
white surface residue around the edges with few spots in the
center

No visible change

Neoprene

Deposits of clear residue

No visible change

Polycarbonate

Slight white residue

No visible change

Polystyrene

Small amt of white residue

No visible change

Polyurethane

Clear, unrinsed - few spots small of white surface residue

No visible change

PVC Plastic

Unrinsed - Small to med spots of white surface residue, rinsed
- no visible changes

No visible change

All other plastic materials showed minimal residue.

-------
(a)

(b)

Figure 3-8. pH-Amended bleach immersed materials of (a) unrinsed neoprene, (b) rinsed
neoprene, (c) unrinsed acrylic, and (d) rinsed acrylic

3.1.3 Other Material (Laminates, Caulk)

A white particulate residue was visible on all the laminate floor coupons that were not rinsed, but
when the rinsing step was applied, the residue was not present. The residue appeared to be
more predominant on the coupons exposed to the chlorine-based SLS. Refer to Figure 3-9 for
example photographs taken at 2 months post exposure of the laminate floor coupons for those
exposed to DB and PAA. There were no discernable visible impacts to the laminate sheet or
silicone caulk for any of the four SLSs, whether rinsed or not.

-------
Figure 3-9. Laminate plank coupons at 2 months after (a) dilute bleach unrinsed, (b) DB
rinsed, and (c) PAA unrinsed (d) PAA rinsed

3.1.4 Small Electrical Equipment
Switch boxes:

The electrical switch boxes were only minimally impacted by the four SLSs. Visual changes for
switch boxes were limited to white residue and a slight red discoloration on the cut edges of
some of the switch boxes. Visual changes were present to a higher degree on the unrinsed
units. The switch boxes sprayed with dichlor appeared to have been impacted the most in terms
of corrosion on the edges, while the PAA appeared to have the least visual impact. See Figure
3-10 below for photographs of the top of the control and unrinsed switch boxes at 2 months post
exposure.

-------
Figure 3-10. Electrical switch box at 2 months after (a) control, (b) dichlor unrinsed, (c) DB
unrinsed, (d) PAA unrinsed, and (e) PAB unrinsed

Circuit breakers

The primary visual impact of the SLS on the circuit breakers was the deposition of a white
residue. This effect was more pronounced on the unrinsed breakers. The breakers sprayed with
the chlorine-based SLS—in particular dichlor—had the most residue, while the PAA appeared
to leave minimal to no residue. The side surfaces of the breakers showed minimal buildup of
residue, suggesting the spray may not penetrate past the front surface when installed in an
electric panel. Figure 3-11 below shows photographs of the front of the circuit breakers for the
control and unrinsed SLS at 2 months post exposure.

-------
Figure 3-11. Circuit breakers at 2 months after (a) control, (b) dichlor unrinsed, (c) DB
unrinsed, (d) PAA unrinsed, and (e) PAB unrinsed

-------
Single-board computers:

The primary visual impact to the single-board computers was the deposition of moderate
amounts of white residue on the cases. For the cases where there was residue, rinsing tended
to remove most of it. As with the circuit breakers, the residue was most prominent with the
chlorine-based SLS, and in particular, the dichlor decontaminant. None of the circuit boards had
any residue with any of the SLSs or rinse conditions, which was expected since the board was
enclosed in its case. Regarding the HDMI 1 and A/V ports, none of the computers showed any
discoloration (which would be indicative of corrosion), although there was some residue visible
for the some of the unrinsed dichlor computers. The exposed USB and ethernet ports did show
some slight discoloration for some units, but this depended on the SLS and rinse condition.
Table 3-10 summarizes the visual changes observed for the single-board computers two
months after the each SLS spray application.

Table 3-10. Summary of Visual Changes to single-board computers

Equipment

Unrinsed

Rinsed

dichlor

Moderate white residue on case; circuit board
pins in open ports show slight discoloration,
pins in closed ports are unchanged

Slight white residue on case and none on
circuit board; pins in open ports show slight
discoloration, pins in closed ports are
unchanged

Diluted bleach

Moderate amount of white residue on case
with no visual changes on circuit board. Metal
pins in open ports show slight discoloration,
pins in closed ports are unchanged

No visual change on case or circuit board.
Metal pins in open ports show slight
discoloration, pins in closed ports are
unchanged

PAA

No visual changes

PAB

Moderate white residue on case. Metal pins in
ports left open show slight discoloration, pins
in closed ports are unchanged

No visual change on case or circuit board.
Metal pins in open ports show slight
discoloration, pins in closed ports are
unchanged

Figure 3-12 shows photographs of the USB and ethernet ports for the single-board computers,
two months after exposure to each SLS. Note that the top USB ports were open during the
spray procedure and the bottom ports were sealed with chemical tape.

-------
Figure 3-12. single-board computer, USB port side at 2 months after (a) control, (b) dichlor
unrinsed, (c) dichlor rinsed, (d) DB unrinsed, (e) DB rinsed, (f) PAA unrinsed, (g) PAA
rinsed, (h) PAB unrinsed, and (i) PAB rinsed

3.3 Equipment functionality results

3.3.1 Single-board computers

As previously discussed, Stressberry is a free software tool that stresses the single-board
computer processor by operating it at high frequency to increase the temperature of the CPU.
The data generated by Stressberry include the initial and final processor temperatures. This
average increase in processor temperature is used as an indicator of any change in the
computer's performance. Initial processor temperatures as measured at baseline, for all the
computers, ranged from 36 - 47 °C, while final processor temperatures at baseline ranged from

-------
52 - 59 °C.

The temperature increase for the control units averaged 15°C (± 1.4 SD) and was relatively
stable over the duration of the 2-month evaluation period, as shown in Figure 3-13. Computers
exposed to diluted bleach and dichlor (both rinsed and non-rinsed) showed drops in the average
temperature change following baseline tests, whereas computers exposed to PAA and PAB
showed an increase or minimal difference in the temperature change following baseline tests.
The temperature changes eventually returned to near baseline conditions for the computers
exposed to diluted bleach and dichlor. The PAB exposed computers' processor temperature
increases were generally stable for the 2 months of tests.

-------
25

(Die
Ctf) 1D

C
CD
-C

CD
l_

(D
Q.

W c

Control

diluted
bleach,
unrinsed

diluted
bleach,
rinsed

djchlor,
unrinsed

diclllor,
rinsed

PAA, PAA, rinsed PAB, PAB, rinsed
unrinsed unrinsed

SLS (Rinse Condition)

I Baseline ¦ Day 1 BWeekl ¦ Month 1 ¦ Month 2

Figure 3-13. Stressberry Test Results - Average Temperature Change (°C ± SD)

The memory execution test was performed to identify variations, if any, in the time required to
repeatedly read and write a large data file. The average memory execution time was determined
by averaging the execution times for each triplicate set of computers. Figure 3-14 provides a
visual representation of the average process execution times for each set of single-board
computers.

The single-board computers performed consistently across SLSs, rinse conditions, and time
post-exposure to the SLS, with individual memory execution times ranging from 0.51 to 0.63
seconds. The SLS or rinse condition didn't appear to have any substantial impact on memory
execution times. It is noted that a small increase in memory execution times was observed on
Day-1 post-exposure for each SLS, although in most instances, by 1-week post-exposure, the
execution times returned to baseline levels. In addition, nearly all the single-board computers
exhibited memory execution times at the 2-month mark that were lower than baseline execution
times.

-------

¦ -j-

Control diluted diluted dichlor dichlor PAA PAA PAB PAB
bleach bleach (unrinsed) (rinsed) (unrinsed) (rinsed) (unrinsed) (rinsed)
(unrinsed) (rinsed)

SLS (Rinse condition)

¦ Baseline ¦ Day 1 BWeekl I Month 1 ¦ Month 2

Figure 3-14. Sysbench average memory execution (s ± SD)

The process execution test was performed to identify changes, if any, in the time required for
the processor to execute the same set of commands numerous times. The average process
execution was determined by averaging the process execution times for each triplicate set of
computers.

Except for the diluted bleach single-board computer sets, execution time was relatively
consistent regardless of the decontaminant or rinse configuration. Unrinsed single-board
computers sprayed with diluted bleach showed a small increase in the average process
execution time (approximately 0.2 s). While the increase persisted for at least the initial 2-
months post-exposure, it is unclear if it is significant.

Computers exposed to the diluted bleach spray with rinse showed a significant change in the
average process execution time at 1-day post-exposure. Of the 127 process execution
measurements recorded in the study, all were within 62 seconds, except for the first replicate of
the rinsed diluted bleach set (64.117 s) and the third replicate of the unrinsed diluted bleach set
(63.0825 s). While the cause for the anomalies cannot be determined, both outliers occurred at
1-day post-exposure and may be caused by residual moisture from the spray event on the
previous day.

Figure 3-15 provides a visual representation of the Sysbench average process execution times
for each set of computers.

-------
63.4

63.3

63.2
63.1

2 62.9

.i 62.8

62.7
62.6

62.5

62.4

62.3

Control

diluted
bleach

diluted dichlor dichlor

PAA

PAB

T I

bleach (unrinsed) (rinsed) (unrinsed) (rinsed) (unrinsed)

PAB
(rinsed)

(unrinsed) (rinsed)

SLS (Rinse condition)

I Baseline ¦ Day 1 BWeekl ¦ Month 1 ¦ Month 2

Figure 3-15. Sysbench average process execution (s ± SD)

Computer failures: Two single-board computers were not functioning prior to exposure to an
SLS. In both cases, the systems were unable to boot. Troubleshooting measures were used
with no success. The units were replaced with functioning computers prior to exposure to the
SLS.

A computer sprayed with diluted bleach (no rinse) and a unit sprayed with diluted bleach (with
rinse) were both unresponsive at 1-week post-exposure. Their SD cards were removed, their
contacts were cleaned, and the cards were reinserted into their slots. This remedy proved
successful and functionality testing resumed. There were no subsequent issues with the
unrinsed unit.

Refer to Figure 3-16 showing the SD card for one of these computers.

The rinsed, diluted bleach unit mentioned above malfunctioned again at Month 1 and was not
able to be recovered with troubleshooting efforts. Another unit sprayed with PAB then rinsed
malfunctioned at Month 2.

-------
ConoKit BconoKit I Conn Kit

241 -RP-DC-1 -02

Raspberry Pi Dichlor
Rinsed 02

241-RP-DC-1-02

Raspberry Pi Dichlor
Rinsed 02

Figure 3-16. Example of SD card at (a) baseline; (b) 1 day after exposure to dichlor and
rinse procedure, but prior to wiping SD card; and (c) 1 week post exposure and after

wiping of SD card

-------
3.3.2 Circuit breakers

Circuit breaker functionality was quantified by the time (s) required to trip the 10-amp circuit
breakers when placed under a 12-amp load. The average trip time was determined by
averaging the time required to trip each of 3 replicate breakers while operating under the
continuous 12-amp load.

Overall, there were no failures of any of the circuit breakers, and in general, average trip times
were consistent across SLS, rinse condition, and post-exposure time. Trip times for Day 1 tests
increased from baseline conditions for the control breakers as well as for the breakers exposed
to dichlor and diluted bleach, although the increases were most likely not significant. (Although it
is acknowledged there were not enough data to conduct a statistical analysis to make this
determination.) The trip times for both rinsed and unrinsed units exposed to PAB decreased
over time.

200
190
180

170

Control dichlor, dichlor, diluted diluted PAB, PAB, PAA, PAA,
unrinsed rinsed bleach, bleach, unrinsed rinsed unrinsed rinsed
unrinsed rinsed

SLS, rinse condition
¦ Baseline ¦ Day 1 ¦ Day7 ¦ Month 1 ¦ Month 2

Figure 3-17. Circuit breaker average trip times (s ± SD)

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3.4 Assessment of Experimental Variables

As discussed in Section 2.9, the visual change scoring system was developed to standardize
the process of assessing visual damages to different material types and test conditions over an
extended period. Scores ranged from 1 to 5, where 1 indicates no visual changes observed
from baseline and 5 indicates the entire surface was impacted.

It is important to note that this scoring system does not differentiate between superficial
changes from the presence of residue or substantive damage to the surface from corrosion. See
Sections 3.1 and 3.2 for details relating to superficial and irreversible damage.

3.4.1 Impact as a Function of Material Type

Most materials showed either no visual change (225 counts with score of 1) or a visible change
of less than 25% of their surface (104 counts with score of 2). Materials with visual changes to
over 75% of their surface included brass (12 counts of score 5), bronze (12 counts of score 5),
copper (14 counts of score 5), and low-carbon steel (9 counts of score 5). Copper and the
copper alloys (bronze and brass) had the highest weighted scores, all > 70, indicating these
materials sustained the most impact. Low carbon steel had the next highest weighted average
at 59. The plastic materials, laminates, and silicone caulk generally all had relatively low
weighted scores. The plastic with the highest weighted score was neoprene (33). Table 3-15
summarizes the score for each material and equipment.

-------
Table 3-15. Visual Impact as a Function of Material

Material

Count of Scores

Weighted
score

Aluminum

Acrylic (plexiglass)

Acrylonitrile butadiene styrene

Brass

Bronze

Butyl rubber

Circuit breaker

Copper

HDPE

Laminate flooring

Laminate sheet

Low-carbon steel

Neoprene

Nylon

Polycarbonate

Polyester film

Polypropylene

Polystyrene

Polyurethane

PVC Plastic

Single-board computer

Silicone caulk

Stainless steel

Steel switch box

Tin

Zinc-Galvanized Low-Carbon Steel

Grand Total

225

104

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3.4.2 Impacts as a Function of Time

Evaluations were performed on test materials and equipment at five time points following
exposure to the SLS. The visual impacts at two time points, 1-week and 2-months post
exposure, are shown in Table 3-16. The 1-week and 2-months impact score trends closely
mirror each other, suggesting that physical changes on material surfaces are stable over time
after some initial point. Percent differences between the 1-week and 2-month scores range from
13% to 35%.

Table 3-16. Impact as a Function of Time

Elapsed Time from Exposure

Count of Scores

Total

1 Week

115

208

2 Months

110

208

Grand Total

225

104

Percent Difference (%)

6.22

3.4.3 Impact by Decontaminant

Application of dichlor caused the highest impact to materials with 63 counts of scores > 2, and
with a weighted score of 221. After dichlor, PAB had the next highest impact, with a weighted
score of 216. Interestingly, the similar high scores/impact of dichlor and PAB are associated
with the decontaminants having a more neutral pH and thus higher levels of hypochlorous acid.
Of the chlorine based SLSs, diluted bleach (typical pH of around 11) had the least impact, with a
weighted score of 202. PAA had the lowest weighted score of the four decontaminants, at 80,
indicating this decontaminant had the least overall visual impact on materials. Although PAA
has a low pH indicative of a strong acid, its relatively lower impacts may be due to the lack of
the reactive chlorine molecule. Refer to Table 3-17 for a summary of these results.

Table 3-17. Impact as a Function of Sporicidal Liquid Solution

Count of Scores

Decontaminant

Total count

Weighted
score

Control

104

dichlor

104

221

diluted bleach

104

202

PAA

104

180

PAB

104

216

Grand Total

329

104

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3.4.4 Impact as Function of Rinsing

In approximately 80% of the cases, visible changes that occurred in coupons that had 25%-50%
of their surface impacted by SLS immersion (score of 2 or 3) could be reversed by performing
the rinse procedure immediately after immersion. In most cases these changes were superficial
changes from residue of dried SLS or reaction products between the material and the SLS.
Alternatively, only about 22% of the cases with visible changes on 75% - 100% (score of 5) of
their surface were reversed by rinsing. For most of the coupons that incurred damage to a large
portion of their surface, the damage was substantial and permanent (e.g., rust and patina). As
shown in Table 3-18, materials that were rinsed had an overall weighted score of 342, while
those that were not rinsed had a score of 477. The number of cases with a score of 1 increased
substantially (more than doubled) after rinsing.

Table 3-18. Impact as a Function of Rinsing

Rinsed Condition

Count of Scores

Weighted score

Rinsed

158

342

Unrinsed

477

Grand Total

225

104

3.5 Wipe Tests for Residue

Using the same scoring approach as discussed in Section 3.4, scores for wiped and unwiped
coupons of the materials selected for this test are summarized in Table 3-19. In general, like the
rinse procedure, the visual changes for coupons that scored in the 25% or under range (score of
1) were from the white residue. After applying the wipe procedure, the number of coupons
determined to have no visual changes increased by 28%. The number of coupons with visual
changes on more than 75% of their surface (score of 5) remained consistent after applying the
wipe procedure. The physical changes resulting from SLS immersion are persistent at this level
of damage and would mostly be indicative of corrosion and not easily mitigated with wiping. In
examining individual materials, those which had weighted scores lowered after wiping were
mostly the plastic materials and would be indicative of the presence of a residue that could be
removed easily. The stainless steel and galvanized steel materials had no change in their
weighted scores after wiping, suggesting no residue or corrosion present. Interestingly, copper's
weighted score increased after wiping, suggesting that the action of wiping revealed more
corrosion that may have been obscured previously; or, that the wipe procedure moved the
residue or corrosion by-products in such a way that more of the surface was covered. Figure 3-
18 shows as an example the low carbon steel coupons exposed to dichlor, before and after the
wipe procedure. Future research is recommended to conduct chemical analyses of the residue.

-------
Table 3-19. Scores Comparing Wiped and Unwiped Coupons

Materials

Counl

of Scores

Total
weighted
score

Aluminum, unwiped

Aluminum, wiped

Acrylic (plexiglass), unwiped

Acrylic (plexiglass), wiped

Butyl rubber, unwiped

Butyl rubber, wiped

Copper, unwiped

Copper, wiped

laminate sheet, unwiped

laminate sheet, wiped

Neoprene, unwiped

Neoprene, wiped

PVC Plastic, unwiped

PVC Plastic, wiped

Stainless steel, unwiped

Stainless steel, wiped

Low-Carbon Steel, unwiped

Low-Carbon Steel, wiped

Total, unwiped

170

Total, wiped

154

-------
Figure 3-18. Low carbon steel coupons exposed to dichlor, with and without rinse and
wiping (a) no rinse, no wipe; (b) no rinse, wiped; (c) rinsed, no wipe; and (d) rinsed, wiped

-------
4.0 Quality Assurance

Activities such as equipment calibration checks, analyte certification, and setting acceptance
criteria for critical measurements were designed to ensure that the data met the Data Quality
Objectives (DQOs) assigned to this project.

4.1 Quality Control

Quality control (QC) checks were used to evaluate how well the measurements were taken
compared to a set of standards or operating procedures. QA/QC checks were used to evaluate
the damage, if any, to the exposed test materials. Visual assessment and small equipment
operability were recorded and assessed (3.1). Replicate coupons were included for each set of
test conditions (Section 2.12.2).

The following general QA/QC procedures were applied for each material/SLS impact evaluation:

• All data, material information, and photographs (when available) were
documented for each tested material/SLS.

• Characterization of the decontamination solutions (active ingredient
concentration, and pH) was performed prior to material exposure.

• The pH instrument was operated according to the manufacturer's instruction
manual and daily checks were performed prior to use.

• Test coupons and small sensitive equipment were visually inspected and
compared to the controls of the same material type.

• Test coupons were visually inspected prior to exposure to ensure their
physical appearance and structure were free of prior defects and
representative of each material.

• Once procedural details were established (Month 1), all subsequent photo
documentation was taken under the same lighting, by the same operator, and
with the same photo equipment. Records of the operator, equipment, and
camera settings were recorded for all photo-documentation sessions prior to
adopting an effective photo-documentation procedure.

Analysis equipment was calibrated at the frequency indicated in Table 4-1.

Table 4-1

. Analysis Equipment Calibration Frequency

Equipment

Calibration
Frequency

Calibration Method

Acceptance
Criteria

Pipettes

Annually

Gravimetric

± 1% target value

Top loading balance

Before each use

Compared to Class
S weights

± 0.01% target

Stopwatch

every 30 days in
accordance with
MOP 3154

Compared to official
U.S. time @
time.gov

±1 sec

Scale

Daily

Compared reading
to Class S weights

± 0.1%

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4.1.1 Data Quality Indicators

The data quality indicators (DQIs) listed in Table 4-2 are specific criteria used to quantify how
the testing sequence was to be performed and specify the tolerable level of potential errors
associated with the measurements.

The following measurements were deemed critical to accomplishing the project objectives:

• Active ingredient concentration of each SLS

• FAC concentration

• PAA concentration
pH of the SLS

• Immersion time

• Drying time (time-point used for the material compatibility assessment
Data quality indicators for this investigation are listed in Table 4-2.

Table 4-2. DQIs for Critical Measurements

Critical Measurement

Analysis Method

Accuracy/Precision

Acceptance Criteria

Concentration and volume of
active ingredient (FAC and PAA)

Titration; burette
Volume: volumetric cylinder

±0.05%
±1 ml

± 20% target
concentration value

pH meter

0.1 pH unit

± 20% target value

Volume of sporicidal solution
dispensed

Graduated cylinder

± 0.1 mL

±5%

Dwell time

NIST-traceable stopwatch

± 5 sec per day

± 5 min per target soaking
time

Drying time

NIST-traceable stopwatch

± 5 sec per day

± 1 hour per material
compatibility timepoint

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7.0 References

Archer, J., A. Touati, W. Calfee, S. Lee, L. Mickelsen, L. Oudejans, R. Delafield, D. Aslett, and
A. Abdel-Hady. "Electrostatic Sprayer Efficacy for Personnel PPE Bio Decontamination -
Mannequin Testing". Presented at 2019 EPA Decontamination Conference, Norfolk, VA,
November 19-21, 2019.

Calfee, M.W., Wood, J.P., Mickelsen, L., Kempter, C.J., et al. 2012. "Laboratory evaluation of
large-scale decontamination approaches". J. Appl. Microbiol. Published online, March 5, 2012.
DOI: 10.1111/j.1365-2672.2012.05259.x.

Dixon, W.T. 1966. "Analysis of peracetic acid solutions". Talanta. 13(8): 1199-200.
doi: 10.1016/0039-9140(66)80172-8. PMID: 18959994.

Ryan, S.P., Lee, S.D., Calfee, M.W., Wood, J.P., et al. 2014. "Effect of inoculation method on
the determination of decontamination efficacy against Bacillus spores". World J Microbiol and
Biotechnol. 30: 2609-2623. DOI 10.1007/s11274-014-1684-2.

U.S. EPA. 2006. "Technology Evaluation Report, Evaluation of Spray-Applied Decontamination
Technologies". EPA/600/R-06/146.

U.S. EPA. 2009. "Evaluation of Liquid and Foam Technologies for the Decontamination of B.
anthracis and B. subtilis Spores on Building and Outdoor Materials". EPA/600/R-09/150.

U.S. EPA. 2014. "Parametric Testing of Decontamination Chemistries to Guide
Decontamination Selection I: Peracetic Acid". EPA/600/R-14/332.

U.S. EPA. 2014. "Assessment of the Impact of Decontamination Fumigants on Electronic
Equipment". EPA/600/R-14/316.

U.S. EPA. 2015. "Expedient Approach for Decontamination of Biologicals - Indoor
Environment". EPA 600/R-15/100.

U.S. EPA. 2017. "Low-Concentration Hydrogen Peroxide (LCHP) Vapor for Bioremediation".
EPA/542/R-19/001.

U.S. EPA. 2017A. "Decontamination Options for Sensitive Equipment in Critical Infrastructure
Following a Bacillus anthracis Incident". EPA/600/S-17/166.

U.S. EPA. 2017C. "Evaluation of Commercially-Available Equipment for the Decontamination of
Bacillus anthracis Spores in an Urban Subway System." EPA 600/R-17/156.

U.S. EPA. 2017D. "Underground Transport Restoration (UTR) Operational Technology
Demonstration (OTD)". EPA 600/R-17/272.

U.S. EPA. 2021. "Inactivation of a Bacillus anthracis Spore Surrogate on Outdoor Materials Via
the Spray Application of Sodium Dichloro-s-triazinetrione and Other Chlorine-Based
Decontaminant Solutions". EPA/600/R-21/004.

U.S. EPA. 2022. "Update on Material Compatibility Testing for Decontamination Methods Used
for Bacillus anthracis (Anthrax)". Tech Brief. EPA/600/S-22/008.

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Wood, J.P., Calfee, M.W., Clayton, M., Griffin-Gatchalian, N., and Touati, A. 2011 A. "Optimizing
acidified bleach solutions to improve sporicidal efficacy on building materials". Published online,
October 27, 2011. DOI: 10.1111/j.1472-765X.2011.03162.x.

Wood, J.P., Choi, Y., and Rogers, J.V. 2011B. "Efficacy of liquid spray decontaminants for
inactivation of Bacillus anthracis spores on building and outdoor materials". J. Appl Microbiol.
110: 1262-1273.

Wood, J.P. and Adrion, A.C. 2019. "Review of Decontamination Techniques for the Inactivation
of Bacillus anthracis and Other Spore-Forming Bacteria Associated with Building or Outdoor
Materials". Environmental Science & Technology 53(8): 4045-4062. DOI:
10.1021/acs.est.8b05274.

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