Supporting Information:
Hydrogen Peroxide Vapor as an Indoor
Disinfectant: Removal to Indoor Materials and
Associated Emissions of Organic Compounds
Dustin Poppendieck1,Heidi Hubbard2* and Richard L. Corsi1,3 1 University of Texas at Austin
2 ICF International
1,3 Maseeh College of Engineering and Computer Science, Portland State University
*Corresponding email: [email protected]
1.1.
Materials Analyzed and Chemicals Quantified
Table S.1 lists the materials tested during the experiments, the graph labels, and a short description of the composition of each material.
Preliminary testing indicated that the predominant emissions were C1 to C9 carbonyls and, as such, these were the focus of organic compound sampling and analysis. Table S.2 list the chemicals quantified, which instrument they were quantified on and the average method detection limit for the chemical. Non-quantified chemicals are discussed in Section 1.10.
Table S.1: Materials tested during hydrogen peroxide vapor experiments.
Material Graph Label Typical Composition
Tufted Carpet Carpet, NLL Tufted with nylon fibers coated on the back with SBR latex and a secondary
polypropylene scrim fabric
Level Loop Carpet Carpet, LL Level loop with nylon fibers coated on the back with SBR latex and a secondary polypropylene scrim fabric
Level Loop Nylon Carpet with PVC Backing
Carpet, PVC Nylon face fiber modular carpet tile laminated with a heavy PVC backing Aged Level Looped
carpet Aged Carpet, LL Level loop with nylon fibers coated on the back with SBR latex and a secondary polypropylene scrim fabric
Linoleum1 Linoleum Linseed oil, woodflour, pine rosin, jute and
limestone
Linoleum with Polish Linoleum w/ Polish Polish: Water and acrylic polish Vinyl Composite Tile VCT Limestone, vinyl, resin, pigments Vinyl Composite Tile
with Polish VCT w/ Polish Polish: Water and acrylic polish
Concrete Concrete Concrete: Water: 14.39 lb, Cement: 26.11 lb, Coarse Aggregate:100.00 lb, Fine Aggregate: 77.77 lb; slump : 7" Concrete with Sealer Concrete w/ Sealer Sealer: 50-70% xylene Gypsum Wall Board
Backing1
GWB Backing Calcium sulfate and solvents, resins Gypsum Wall Board
with Flat Vinyl Acrylic Paint1
GWB w/ Flat Paint Paint: Heavy paraffinic oil, quartz, cristobalite, kaolin, calcium carbonate, titanium dioxide, carbon black, ethylene glycol, talc
Paint Primer: Water, vinyl polymer, kaolin, titanium dioxide, calcined clay, talc quartz Gypsum Wall Board
with Satin Eggshell Vinyl Acrylic Paint1
GWB w/ Satin Paint Paint: 2-(2-Butoxyethoxy)-ethanol, ethylene glycol, cristobalite, calcium carbonate, titanium dioxide, carbon black, kaolin, talc
Paint Primer: Water, vinyl polymer, kaolin, titanium dioxide, calcined clay, talc quartz Gypsum Wall Board w/
Wallpaper glue: Clay, dextrin, cellulose, biocides, additives
Acoustic Ceiling Tile1 Ceiling Tile Composed of cornstarch, newsprint,
mineral wool, recycled tires, perlite. Covered with vinyl latex paint. HVAC Duct and Liner -
Unused HVAC Duct Galvanized metal with oil layer from galvanizing and fabricating processes; glue layer between liner and duct; liner is comprised of fiberglass and solvents with a thermoset resin and acrylic coating
HVAC Duct and Liner -
in-situ Aged HVAC Duct See HVAC Duct
Medium Density
Fiberboard1 MDF Thermomechanical pulp (cellulose, lignin, hemicellulose), wax, and
phenol-formaldehyde resin
Particle Board1 Particle Board Wood particles, wood fibers, and synthetic
resins Particle board with
Laminate Particle Board w/ Laminate Melamine-impregnated, alpha cellulose overlay and decorative surface papers, superimposed over wood particles, wood fibers, and synthetic resins
Office Partition1 Office Partition Modified urethane acrylate adhesive
(acrylated monomer, hydroxy alkyl methocrylate, acrylic acid, silica dioxide, organic peroxide), steel tubes, fiberglass, polyester fabric, PVC
Painted Metal (filing
cabinets) 1 Filing Cabinet Baked enamel finish over rust-inhibiting
phosphate over stainless steel Paper – 50 Stacked
Sheets of Plain, Unused Copier Paper
Paper Paper: Pulp (cellulose and hemicellulose), calcium carbonate, pigments, titanium dioxide, starch, clay, rosin, AKD (alkylketene dimer)
Paper - 50 Stacked Sheets of Used Copier Paper
Paper w/ Toner Toner: styrene acrylic copolymer (50-100%), Iron oxide (25-50%), Polypropylene (1-5%), Dyes (1-5%)
1Edge and back coated with sodium silicate 2Edge coated with sodium silicate
Table S.2: Carbonyls quantified during hydrogen peroxide vapor experiments.
Chemical Formula Structure Analysis Method
Average MDL1 g/m3 Formaldehyde CH2O HPLC 1.3 Acetaldehyde C2H4O HPLC 1.5 Acetone C3H6O HPLC 2.8 Acrolein C3H4O HPLC 1.4 Propanal C3H6O HPLC 2.3 Butanal C4H8O HPLC 2.2 Butenal C4H6O HPLC 2.1 Pentanal C5H10O HPLC 4.4 Isopentanal C5H10O HPLC 2.1 Hexanal C6H12O HPLC 2.9 Benzaldehyde C7H6O HPLC 1.6 2,5-Dimethylbenzaldehyde (2,5-DMB) C9H10O HPLC 1.4 o-Tolualdehyde C8H8O GCMS 2.7 Heptanal C7H14O GCMS 1.6 Octanal C8H16O GCMS 12.1 Nonanal C9H18O GCMS
1.2.
Analytical System
Experiments were completed using 48-L chambers, within which 23 building materials were individually exposed to vaporous hydrogen peroxide (VHP) at typical disinfection concentrations (Figure S.1). After materials were placed in the chambers, the face plate of each chamber was sealed with a Viton gasket and 20 wing nuts. VHP was generated using a Bioquell ClarusTM-C generator operated in closed-loop mode. For this study it
was necessary to de-humidify the return air side of the loop. Variations in hydrogen peroxide vapor delivery concentration existed as the temperature of the condensation system varied during experiments. Approximately 6 L min-1 of air was injected into the
closed loop using a zero-air generator. All transfer lines were wrapped in heat tape maintained at 55 ºC to 70 ºC to minimize condensation. The inlet air temperature was generally around 50 ºC and the inlet relative humidity was saturated (100%) at this temperature. Given that the exterior wall temperatures of chambers during experiments were close to room temperature (~25 ºC), it is reasonable to assume that the temperature in chambers was significantly less than 50 ºC, the relative humidity remained at 100%, and condensation did occur. Switching of sample analysis streams between chambers was performed manually throughout all experiments. Switching valves were housed in an oven maintained at 60 ºC. During the disinfection phase, switching valves were manually changed every two minutes for six hours in order to determine hydrogen peroxide vapor concentrations in the inlet stream, exit of all three chambers, and reference (zero) air. Inlet and outlet hydrogen peroxide vapor concentrations were quantified using an on-line continuous monitoring system based on infrared absorption analysis of hydrogen peroxide.
Figure S.1: Schematic of experimental system configuration for VHP experiments. S exhaust S = = flow meter = valve = ozone scrubber = DNPH/Tenax = sample pump vaporized hydrogen peroxide generator chamber 2 chamber 1 S S control chamber S zero air generator Vaporize Hydrogen Peroxide Monitor ~6 L/min condenser ~244L/min = heated line = ambient line = cooled line
1.3.
Analytical Parameters
Carbonyls were sampled using Waters Sep-pak DNPH cartridges. After extraction with Carbonyls were analyzed using High-performance liquid chromatography ultraviolet (HPLC-UV) using the method highlighted in Table S.3, where solution A is 100 % acetonitrile and solution B is 30% acetonitrile in water, by volume. Other chemicals were sampled using Tenax sorption tubes and analyzed using thermal desorption gas
chromatograph mass spectrometer (TD-GCMS) using the method highlighted in Table S.4.
Table S.3: HPLC flow program. Time
(min) Total Flow (mL/min) % A % B
0 1 0 100 5 1 0 100 10 1 24 76 15 1 30 70 45 1 50 50 50 1 100 0 56 1 0 100
Table S.4:. GCMS program parameters. GC
Column SGE BP-1, 60m, 0.32mm, 1μm
Equilibrium Time 0.25 min
Initial Temperature 40 ºC
Initial Time 3 min
Ramp 10 ºC/min to 150 ºC
20 ºC/min to 285 ºC
Final Time 5.17 min
MS Mode
Scan Range 350-550 AMUScan
Scan Rate 2.39 /sec
Scan Delay 3.5 min
TD
Equilibrium Time 0 min
Ramp 10 ºC/sec to 250 ºC
Total Time 27.0 min
Initial Pressure 10 psi
Initial Time - Pressure 2.5 min
Ramp 3 to 14
From 2.5 to 27 psi min
1.4.
Data Analysis for Hydrogen Peroxide Deposition
Hydrogen peroxide deposition velocities (Vd) for each control and each building material
were determined based on a mass balance on each chamber. Previous tracer gas studies and the control chamber concentrations observed in this study indicate that well-mixed conditions existed inside the chambers. Equation S.1 was used as the governing equation for VHP concentration inside each well-mixed chamber:
Equation S.1 where C is the VHP concentration inside the chamber (and in the chamber exhaust stream) (mg m-3), C
o is the VHP concentration entering the chamber (mg m-3), is the air
exchange rate of the chamber (hr-1), V
d is the hydrogen peroxide deposition velocity to
the material sample in the chamber (m hr-1), V
d,ss is the hydrogen peroxide deposition
velocity to the stainless steel walls of the chamber (m hr-1) as determined from control
chamber experiments, A is the projected exposed area of the material sample (m2), A ss is
the total exposed area of the stainless-steel walls of the chamber (m2), and V is the
volume of the chamber minus the volume occupied by the material sample (m3). This
analysis assumes no losses to homogeneous gaseous decay. The air exchange rate was measured by dividing the average air flow rate through the chamber by the chamber volume.
Equation S.1 was re-written in discrete form as shown by Equation S.2:
𝑪𝒏+𝟏― 𝑪𝒏 𝜟𝒕 = 𝝀 𝟐
[
𝑪𝒐 𝒏+𝟏+𝑪𝒏 𝒐]
― 𝝀 𝟐[
𝑪 𝒏+𝟏+𝑪𝒏]
― 𝑽 𝒅(
𝒕=𝒕𝒂𝒗𝒆)
𝑨 𝟐𝑽[
𝑪 𝒏+𝟏+𝑪𝒏]
― 𝑽𝒅,𝒔𝒔 ` Equation S.2(
𝒕=𝒕𝒂𝒗𝒆)
𝑨𝒔𝒔𝟐𝑽[
𝑪𝒏+𝟏+𝑪𝒏]
V A C V V A C V C C dt dC ss ss d d o , where n and n+1 indicate consecutive data points and tave is the time midway between the
times corresponding to data points at n and n+1. Equation S.2 as solved for Vd as follows:
Equation 𝑽𝒅
(
𝒕=𝒕𝒂𝒗𝒆)
= 𝟐 𝜟𝒕[𝑪𝒏― 𝑪𝒏+𝟏] +𝝀[𝑪𝒏𝒐+𝟏+𝑪𝒏𝒐― 𝑪𝒏+𝟏― 𝑪𝒏]― 𝑽𝒅,𝒔𝒔(𝒕=𝒕𝒂𝒗𝒆) 𝑨𝒔𝒔 𝑽[𝑪𝒏+𝟏+𝑪𝒏] 𝑨 𝑽[𝑪𝒏+𝟏+𝑪𝒏] S.3Where the deposition velocity to chamber walls, Vd,ss, was calculated using Equation S.4:
Equation S.4 𝑽𝒅,𝒔𝒔(𝒕=𝒕𝒂𝒗𝒆) = 𝟐 𝜟𝒕[𝑪𝒏― 𝑪𝒏+𝟏] +𝝀[𝑪𝒐𝒏+𝟏+𝑪𝒏𝒐― 𝑪𝒏+𝟏― 𝑪𝒏] 𝑨𝒔𝒔 𝑽[𝑪𝒏+𝟏+𝑪𝒏]
The time varying deposition velocity for each material was obtained by solving Equation S.3 for each consecutive pair of concentration data points.
1.5.
Hydrogen Peroxide Vapor Deposition Data
Temporal variations in VHP concentration for every experiment are presented in Figure S.2 through Figure S.19. Each figure shows a set of data from a three-chamber
experiment (two materials and empty control chamber). The vertical line at 9 hours indicates when the hydrogen peroxide generator was switched on. The vertical line at 13 hours is when the hydrogen peroxide generator was switched off. The vertical and
horizontal axes are scaled consistently between each plot except for the plots that relate to low and high VHP concentrations. The aged level loop carpet and aged HVAC
experiment last only 1.5 hours, while the gypsum wallboard with wallpaper and gypsum wallboard backing experiment lasted 5 hours.
0 250 500 750 1000 8 9 10 11 12 13 14 Experimental Time (hr) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control Paper w/ Toner Paper
Figure S.2: VHP concentration profile for paper with toner and paper. Green and red lines indicate the beginning and end of VHP generation.
0 250 500 750 1000 1250 8 9 10 11 12 13 14 Experimental Time (hr) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control VCT W/ Polish VCT
Figure S.3: VHP concentration profile for vinyl composite tile with polish and vinyl composite tile. Green and red lines indicate the beginning and end of VHP generation.
0 250 500 750 1000 1250 8 9 10 11 12 13 14 Experimental Time (hr) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control MDF Particleboard
Figure S.4: VHP concentration profile for medium density fiberboard and particleboard. Green and red lines indicate the beginning and end of VHP generation. 0 250 500 750 1000 1250 8 9 10 11 12 13 14 Experimental Time (hr) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control Carpet, T Carpet, PVC
Figure S.5: VHP concentration profile for PVC backed carpet and tufted carpet. Green and red lines indicate the beginning and end of VHP
0 250 500 750 1000 8 9 10 11 12 13 14 Experimental Time (hr) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control GWB w/ Satin Paint GWB w/ Flat Paint
Figure S.6: VHP concentration profile for gypsum wallboard with satin paint and gypsum wallboard with flat paint. Green and red lines indicate the beginning and end of VHP generation.
0 250 500 750 1000 1250 8 9 10 11 12 13 14 15 Experimental Time (hr) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control GWB w/ Wallpaper GWB Backing
Figure S.7: VHP concentration profile for gypsum wallboard with wallpaper and gypsum wallboard backing. Green and red lines indicate the
0 250 500 750 1000 1250 8 9 10 11 12 13 14 Experimental Time (hr) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control Concrete w/ Sealer Concrete
Figure S.8: VHP concentration profile for concrete with sealer and concrete. Green and red lines indicate the beginning and end of VHP generation. 0 250 500 750 1000 1250 8 9 10 11 12 13 14 Experimental Time (hr) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control Linoleum w/ Polish Carpet, LL
Figure S.9: VHP concentration profile for linoleum with polish and level loop carpet. Green and red lines indicate the beginning and end of VHP generation.
0 250 500 750 1000 8 9 10 11 12 13 14 Experimental Time (hrs) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control
Metal File Cabinet Ceiling Tile
Figure S.10: VHP concentration profile for ceiling tile and metal file cabinet. Green and red lines indicate the beginning and end of VHP generation. 0 250 500 750 1000 1250 8 9 10 11 12 13 14 Experimental Time (hr) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control Linoleum HVAC Duct
Figure S.11: VHP concentration profile for linoleum and HVAC duct. Green and red lines indicate the beginning and end of VHP generation.
0 250 500 750 1000 1250 8 9 10 11 12 13 14 Experimental Time (hr) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control
Aged HVAC Duct Aged Carpet, LL
Figure S.12: VHP concentration profile for aged level loop carpet and aged HVAC duct. Green and red lines indicate the beginning and end of VHP generation. 0 250 500 750 1000 1250 8 9 10 11 12 13 14 Experimental Time (hr) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control MDF w/ Laminate Office Partition
Figure S.13: VHP concentration profile for medium density fiberboard with laminate and office partition. Green and red lines indicate the beginning and end of VHP generation.
0 250 500 750 1000 8 9 10 11 12 13 14 Experimental Time (hr) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control
Aged HVAC Duct, Duplicate Aged Carpet, LL, Duplicate
Figure S.14: VHP concentration profile for aged level loop carpet and aged HVAC duct. Green and red lines indicate the beginning and end of VHP generation. 0 250 500 750 1000 1250 8 9 10 11 12 13 14 Experimental Time (hr) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control GWB w/ Wallpaper, Duplicate GWB Backing, Duplicate
Figure S.15: VHP concentration profile for duplicate gypsum wallboard with wallpaper and duplicate gypsum wallboard backing. Green and red lines indicate the beginning and end of VHP generation.
0 250 500 750 1000 1250 8 9 10 11 12 13 14 Experimental Time (hr) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control Particleboard, Duplicate Concrete, Duplicate
Figure S.16: VHP concentration profile for duplicate particleboard and duplicate concrete. Green and red lines indicate the beginning and end of VHP generation. 0 250 500 750 1000 1250 8 9 10 11 12 13 14 Experimental Time (hr) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control
Paper w/ Toner, Low AER Ceiling Tile, Low AER
Figure S.17: VHP concentration profile for ceiling tile and paper with toner at low air exchange rates. Green and red lines indicate the beginning and end of VHP generation.
0 250 500 750 1000 8 9 10 11 12 13 14 Experimental Time (hr) H yd ro g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control
Paper w/ Toner, Low Input Carpet, LL, Low Input
Figure S.18: VHP concentration profile for level loop carpet and paper with toner at low input concentration. Green and red lines indicate the beginning and end of VHP generation.
0 250 500 750 1000 1250 8 9 10 11 12 13 14 Experimental Time (hr) H yd o g en P er o xi d e C o n ce n tr at io n ( p p m ) Input Control
Ceiling Tile, Low Input HVAC Duct, Low Input
Figure S.19: VHP concentration profile for ceiling tile and HVAC duct at low input concentration. Green and red lines indicate the beginning and end of VHP generation.
1.6.
Deposition Velocities
Temporal variations in deposition velocities for VHP are presented in Figure S.20
through Figure S.24. Data are presented as the running average of every three data points and are plotted on a logarithmic vertical axis. Gaps in the solid line correspond to
negative values. Negative values were the result of the sensitivity of Equation S.3 to decreases between consecutive concentration data points relative to concentration
changes in the control chamber. Average steady state deposition velocity values for each material are listed in Table S.5.
1 10 100 1,000 10,000 9 10 11 12 13 14 Experitmental Time (hr) H yd ro g en P er o xi d e D ep o si ti o n V el o ci ty ( cm /h r) Carpet, PVC Carpet, T Office Partition Concrete Ceiling Tile
Figure S.20: VHP deposition velocity for PVC backed carpet, tufted carpet, office partition, concrete, and ceiling tile.
1 10 100 1,000 9 10 11 12 13 14 Experitmental Time (hr) H yd ro g en P er o xi d e D ep o si ti o n V el o ci ty ( cm /h r) Aged Carpet, LL Concrete w/ Sealer HVAC Duct Paper w/ Toner MDF w/ Laminate
Figure S.21: VHP deposition velocity for aged level loop carpet, concrete with sealer, HVAC duct, paper with toner, and medium density fiberboard with laminate. 1 10 100 1,000 10,000 9 10 11 12 13 14 Experitmental Time (hr) H yd ro g en P er o xi d e D ep o si ti o n V el o ci ty ( cm /h r) Paper GWB w/ Flat Paint Carpet, LL Particle Board Linoleum
Figure S.22: VHP deposition velocity for paper, gypsum wallboard with flat paint, level loop carpet, particle board, and linoleum.
1 10 100 1,000 10,000 9 10 11 12 13 14 Experitmental Time (hr) H yd ro g en P er o xi d e D ep o si ti o n V el o ci ty ( cm /h r)
Aged HVAC Duct MDF
GWB w/ Satin Paint GWB Backing Linoleum w/ Polish
Figure S.23: VHP deposition velocity for aged HVAC duct, medium density fiber board, gypsum wallboard with satin paint, gypsum wallboard backing, and linoleum with polish.
1 10 100 1,000 10,000 9 10 11 12 13 14 Experitmental Time (hr) H yd ro g en P er o xi d e D ep o si ti o n V el o ci ty ( cm /h r)
Metal File Cabinet VCT
VCT w/ Polish GWB w/ Wallpaper
Figure S.24: VHP deposition velocity for metal filing cabinet, vinyl composite tile, vinyl composite tile with polish and gypsum wallboard with
Table S.5: Hydrogen peroxide vapor steady state deposition velocities (cm h ).
Material Average Uncertainty2
Control (Chamber Walls)1 10 5
Carpet, NLL/LL 420 105 Carpet, PVC >1200 NA Aged Carpet, LL 940 104 Linoleum 290 65 Linoleum w/ Polish 150 69 VCT 59 98 VCT w/ Polish 0 48 Concrete 810 131 Concrete w/ Sealer 630 106 GWB Backing 440 90 GWB w/ Flat Paint 450 53 GWB w/ Satin Paint 250 37 GWB w/ Wallpaper 54 35 Ceiling Tile 790 96 HVAC Duct 640 75
Aged HVAC Duct 540 79
MDF 220 43
Particle Board 370 45
Particle Board w/ Laminate 480 89
Office Partition >1100 NA
Filing Cabinet 100 37
Paper 380 48
Paper w/ Toner 480 47
1Average and standard deviation of control average values. Chamber wall deposition accounted
for in other values as show in Equation S.3.
2Unceratinty is the sum of the chamber deposition standard deviation of averaged values plus
the net change if the chamber wall deposition was 45% different from the control chamber (45% is the RSD of the control chamber experiments).
1.7.
Comparison of Duplicates – Hydrogen Peroxide
Deposition Velocities
Six duplicate experiments were performed (Figure S.25 and Figure S.26). The steady-state deposition velocities were within 30% for five of six materials and for four of the six duplicates were not statistically different (student t test, P > 0.01). The one exception was wallpaper on gypsum wallboard, which had a large relative difference. However, the deposition velocities for this material were small, and thus prone to magnification of differences in duplicates; the absolute differences in duplicate deposition velocities for this material were small. Differences in the two duplicate experiments are primarily attributed to heterogeneity in building materials and variation in input concentrations.
1 10 100 1,000 10,000 9 10 11 12 13 14 Experitmental Time (hr) H yd ro g en P er o xi d e D ep o si ti o n V el o ci ty ( cm /h r) Concrete Concrete, Duplicate Particle Board
Particle Board, Duplicate Aged HVAC Duct
Aged HVAC Duct, Duplicate
Figure S.25: Comparison of deposition velocities for duplicate concrete, aged HVAC duct and particle board.
1 10 100 1,000 9 10 11 12 13 14 Experitmental Time (hr) H yd ro g en P er o xi d e D ep o si ti o n V el o ci ty ( cm /h r) Aged Carpet, LL
Aged Carpet, LL, Duplicate GWB w/ Wallpaper
GWB w/ Wallpaper, Duplicate GWB Backing
GWB Backing, Duplicate
Figure S.26: Comparison of deposition velocities for duplicate aged carpet, gypsum wallboard with wallpaper, and gypsum wallboard backing.
1.8.
Parameter Effects on Hydrogen Peroxide Deposition
Velocities
Four materials were run using a 30% hydrogen peroxide feed solution instead of the standard 50% feed solution (Figure S.27 and Figure S.28). For three of the four materials this resulted in an increase in the deposition velocity (Carpet, LL, HVAC Duct, and Paper w/Toner). The HVAC Duct VHP concentrations were close to the detection limits
(Figure S.19), resulting in limited data in Figure S.27. Assuming the same feed rate of the VHP generator was maintained constant, more water would be introduced into the chambers. This could lead to a water film or a water film with greater depth than
standard experiments. The results in Figure S.27 and Figure S.28 for Carpet, LL, HVAC Duct, and Paper w/Toner are consistent with hydrogen peroxide partitioning into a water film on the material surface, with a greater removal rate with a more extensive water film. The one material where this wasn’t seen was the ceiling tile. Ceiling tiles are typically made out of cornstarch, newsprint, mineral wool, recycled tires, or perlite and covered with vinyl latex paint (Table S.1). Perlite and newsprint can have strong
capillary action and adsorbing significant amounts of water, moving it away from the surface decreasing potential surface water layer structures. The exact composition of the ceiling tile was not recorded.
The deposition velocity model does not explicitly account for partitioning into a water film. If a water layer is built up upon the material surface, the calculated deposition velocity would be an underestimate for higher VHP concentrations.
1 10 100 1,000 10,000 9 10 11 12 13 14 Experitmental Time (hr) H yd ro g en P er o xi d e D ep o si ti o n V el o ci ty ( cm /h r) HVAC Duct
HVAC Duct, Low Input Carpet, LL
Carpet, LL, Low Input
Figure S.27: Comparison of deposition velocities for standard and low hydrogen peroxide inputs for HVAC duct and level loop carpet.
1 10 100 1,000 10,000 9 10 11 12 13 14 Experitmental Time (hr) H yd ro g en P er o xi d e D ep o si ti o n V el o ci ty ( cm /h r) Paper w/ Toner
Paper w/ Toner, Low Input Ceiling Tile
Ceiling Tile, Low Input
Figure S.28: Comparison of deposition velocities for standard and low hydrogen peroxide inputs for paper with toner and ceiling tile.
1.9.
Organic Compound Concentrations
Illustrative temporal variations in organic compound concentrations are shown graphically here for concrete (Figure S.29 for HPLC data and Figure S.30 for GCMS data). On each graph the vertical line at hour 9 indicates when the VHP was introduced to the chamber. Data prior to the green line are background concentrations. Due to interferences with the potassium iodide scrubber, no organic compound samples were taken when the VHP was present in the chamber. The vertical line at hour 13 is when the VHP was switched off. In some cases, an organic compound was positively identified but below the method detection limit (MDL). For purposes of emission rate calculations, the organic compound concentration was set to one-half the measured MDL, i.e., as opposed to zero or the MDL. The choice of approach used to quantify concentrations below MDL had a negligible effect on estimates of the overall organic compound mass releases.
Table S.6 shows the time integrated quantified organic compound mass released for each material, both the individual compounds and the total summed mass of all compounds. GCMS data were not collected for concrete with sealer and the following duplicates: gypsum wallboard with wallpaper, gypsum wallboard backing, and concrete. HPLC data were not collected for the duplicates of aged level loop carpet and aged HVAC duct. Controls for experiments 2, 9, and 11 had elevated background organic compound masses. Without these anomalies the average organic compound mass for the remaining 11 control experiments was 0.05 mg m-2, and the average for all materials was 0.43 mg
m-2. 0.00 0.02 0.04 0.06 0.08 0.10 0 5 10 15 20 25 Experimental Time (hrs) C o n ce n tr at io n ( m g /m 3 ) Heptanal Octanal Nonanal Tolualdehyde
0 0.1 0.2 0.3 0.4 0 10 20 Experimental Time (hrs) C o n ce n tr at io n ( m g /m 3 ) Formaldehyde Acetaldehyde Acetone Propanal Butenal Butanal Isopentanal Pentanal Hexanal Benzaldehyde 2,5 -Dimethylbenzaldehyde
Figure S.30: Temporal organic compound concentrations for concrete (HPLC). Green and red lines indicate the beginning and end of VHP
Table S.6: Time integrated organic compound emissions from each material (mg m-2). Values not displayed indicate the chemical
was not detected. Values of 0.00 indicate the chemical was detected at a low level that rounded to 0.00. Bold values indicate emissions of greater than 0.25 mg m-2 for an individual chemical.
Material Experiment Formaldehyde Aceta
ldehyde
Acetone Propanal Butenal Butanal Isopentanal Pentanal Hexa
n
al
Heptanal Octanal Nonanal Benzaldehyde Tolu
al dehyde 2,5 - Dimethylbenzaldehyde Total Control 1 1 0.01 0.07 0.00 0.01 0.00 0.00 0.10 Paper 1 0.03 0.53 0.56 Paper w/ Toner 1 0.41 0.41 Control 2 2 0.02 0.51 0.01 0.01 0.00 0.00 0.56 VCT 2 0.32 0.06 0.05 0.20 0.01 0.64 VCT w/ Polish 2 0.39 0.06 0.16 0.03 0.64 Particleboard 3 0.01 0.02 0.02 MDF 3 0.23 0.01 0.24 Control 3 3 0.00 0.01 0.00 0.00 0.01 Carpet, Tufted 4 0.00 PVCB Carpet 4 0.10 0.46 0.01 0.03 0.59 Control 4 4 0.01 0.00 0.00 0.00 0.02 Eggshell Paint on GWB 5 0.00 0.00 0.00 0.00 Control 5 5 0.00 0.00 0.00 Flat Paint on GWB 5 0.00 0.00 Wallpaper on GWB, Duplicate1 6 0.00 0.00 0.08 0.08
Material Experiment Formaldehyde Aceta
ldehyde
Acetone Propanal Butenal Butanal Isopentanal Pentanal Hexa
n
al
Heptanal Octanal Nonanal Benzaldehyde Tolu
al dehyde 2,5 - Dimethylbenzaldehyde Total Control 61 6 0.00 0.00 GWB Backing, Duplicate1 6 0.01 0.01 Sealed Concrete1 7 0.18 0.08 0.04 0.03 0.05 0.00 0.00 0.02 0.01 0.41 Concrete, Duplicate1 7 0.62 0.35 0.12 0.13 0.03 0.06 0.02 0.02 1.35 Control 71 7 0.01 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.06 Carpet, LL 8 0.26 0.01 0.22 0.00 0.00 0.00 0.50 Linoleum w/ Polish 8 0.04 0.01 0.01 0.02 0.08 Control 8 8 0.01 0.03 0.01 0.04
Metal File Cabinet 9 0.06 0.00 0.04 0.00 0.10
Ceiling Tile 9 0.11 0.03 0.04 0.46 0.64
Control 9 9 0.00 0.02 0.74 0.01 0.01 0.00 0.00 0.00 0.00 0.07 0.00 0.00 0.86
HVAC Duct 10 1.06 0.23 0.00 0.36 0.02 1.67
Control 10 10 0.11 0.02 0.00 0.00 0.00 0.12 0.25
Linoleum 10 0.52 0.11 0.02 0.03 0.02 0.04 0.74
Aged HVAC Duct, Duplicate2 11 0.00
Aged Carpet, LL, Duplicate2 11 0.00
Control 11;2 11 0.41 1.00 0.19 0.73 2.33
Office Partition 12 0.57 0.03 0.03 0.63
Control 12 12 0.07 0.05 0.00 0.01 0.00 0.00 0.00 0.14
Laminated Fiberboard 12 0.56 0.04 0.01 0.01 0.14 0.01 0.05 0.82
Aged Carpet, LL 13 0.00 0.01 0.02
Material Experiment Formaldehyde Aceta
ldehyde
Acetone Propanal Butenal Butanal Isopentanal Pentanal Hexa
n
al
Heptanal Octanal Nonanal Benzaldehyde Tolu
al dehyde 2,5 - Dimethylbenzaldehyde Total Control 131 13 0.03 0.01 0.00 0.01 0.09 0.01 0.01 0.15 Control 14 14 0.00 0.03 0.00 0.00 0.00 0.00 0.00 0.04 GWB Backing 14 0.02 0.02 0.09 0.05 0.18 Wallpaper on GWB 14 0.04 0.31 0.06 0.40 Concrete 15 1.17 0.01 0.14 0.07 0.20 0.06 0.16 0.03 0.03 1.87 Control15 15 0.00 0.04 0.01 0.01 0.00 0.00 0.00 0.00 0.07 Particleboard, Duplicate 15 0.30 0.03 0.09 0.00 0.00 0.00 0.00 0.43
Ceiling Tile, Low ACH 16 0.03 0.13 0.01 0.03 0.01 0.01 0.01 0.00 0.23
Control 16, Low ACH 16 0.01 0.00 0.01 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.04
Paper w/ Toner, Low ACH 16 0.20 0.42 0.04 0.07 0.01 0.01 0.29 0.00 0.00 1.03
Carpet, LL, Low H2O2 Feed 17 0.06 0.00 0.00 0.07
Control 17, Low H2O2 Feed 17 0.00 0.04 0.02 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.09
Paper w/ Toner, Low H2O2
Feed 17 0.37 0.04 0.38 0.03 0.05 0.87
Ceiling Tile, Low H2O2 Feed 18 0.00 0.00 0.01
Control 18, Low H2O2 Feed 18 0.01 0.02 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.05
HVAC Duct, Low H2O2 Feed 18 0.10 0.03 0.00 0.13
1No GCMS data 2No HPLC data
Three hours after the ozone concentration in each chamber decreased to less than 35 ppm, the hydrogen peroxide detection limit, it was assumed that by-product mass in the chamber was no longer being formed due to hydrogen peroxide vapor-material reactions. This time was defined as the beginning of the persistence phase. If there were no more formation reactions, then a standard homogenous reactor model would predict that the by-product concentration should decay exponentially with the air exchange rate (Equation S.5).
Equation S.5
where C is the BDBP concentration in chamber air and exhaust (mg/m3), C
init is the BDBP
concentration in chamber at the beginning of the persistence phase (mg/m3), k is the first-order
decay constant (hr-1), and t is time (hr). If the BDBP concentration was dependent solely on the
air exchange rate the decay constant should be the same for all materials (provided the air exchange rate is constant). However, when the data were fitted to Equation S.5, the decay constant was highly variable. This indicated that the materials were emitting by-products over time after the hydrogen peroxide vapor was no longer present in the system.
Equation S.5 was solved for the decay constant, which, in turn, was used to solve for the estimated half life (50% removal) of each by-product (t50%, hours):
Equation S.6 It is important to recognize that a first-order exponential decay model is empirical and only fit four data points (data after red line in Figure S.29). Hence, it may lead to underestimates of long-term BDBPs releases if such releases are controlled by non-linear transport processes, e.g., desorption and diffusion from within porous materials. As such, the calculated half-life is not necessarily a precise representation of persistence. However, it does serve as a useful metric to compare the relative persistence of different chemicals from different materials. For
comparisons, the half-lives were characterized in Table S.7 and Table S.8 as low (less than 6.2 days), medium (between 6.2 and 40 days) and high (greater than 40 days).
Many of the chemicals characterize as having high persistence via the half-life analysis had negative decay constants. In other words, for these BDBPs, concentrations increased throughout the persistence phase.
Table S.7: Relative persistence of lighter BDBPs during experiments.
Formaldehyde Acetaldehyde Acetone Propanal Butenal Butanal Isopentanal Pentanal Aged Carpet, LL Low
Carpet, LL
Carpet, PVC Low
Ceiling Tile
Concrete Low Low Low Low Low Low
Concrete w/ Sealer Low Low Low Low Low
GWB w/ Flat Paint High GWB w/ Satin Paint Low GWB w/ Wallpaper
GWB Backing Low
Aged HVAC Duct Low Low
HVAC Duct High
Linoleum Low
Linoleum w/ Polish Low Low
MDF
MDF w/ Laminate Low Low
Metal File Cabinet Low
Office Partition High Low
Paper Low
Paper w/ Toner Low
Particleboard VCT
Table S.8: Relative persistence of heavier BDBPs during experiments.
Hexanal Heptanal Octanal Nonanal Benzaldehyde Tolualdehyde 2,5-Dimethylbenzaldehyde
Aged Carpet, LL Carpet, LL Carpet, PVC
Ceiling Tile Low Low
Concrete High Low Low
Concrete w/ Sealer GWB w/ Flat Paint GWB w/ Satin Paint GWB w/ Wallpaper GWB Backing Aged HVAC Duct
HVAC Duct Low High Low
Linoleum Low Low High Low
Linoleum w/ Polish Low Low
MDF
MDF w/ Laminate
Metal File Cabinet High
Office Partition High Paper
Paper w/ Toner Particleboard
VCT High High
1.10. Non-Quantified Organic Compounds
Compounds detected by GCMS, but not quantified, are described here. For each material, two GCMS chromatograms were analyzed. The first chromatogram was from before the VHP was introduced to the experimental system. The second chromatogram was from a sample obtained after exposure of the test material to VHP, but after the VHP injection had been terminated and the VHP concentration declined to effectively zero. All peaks in each selected chromatogram were integrated, even those for which
chromatographic standards were not employed. Peak ion spectrums were compared to known spectrums to determine possible chemicals that matched the peak spectrum. A summary report of each chromatogram provided a probability that the peak spectrum matched a known library spectrum. Spectrum matches where the probability was greater than 80% are shown in Table S.9.
Table S.9 does not include the by-products that were quantified on the GCMS or the HPLC. In addition, trimethylbenzene isomers were removed from this list as they were frequently found as compounds in laboratory air. Alkanes are also compounds found in laboratory air and are not included in Table S.9, but were present at higher levels during VHP experiments, relative to experiments with other disinfectants. The levels tended to increase the longer a single VHP supply hose was in use. It is possible that the adhesive on the supply hose was degraded, ultimately leading to leaks in the hose, which was a common problem during experiments.
Although the peaks were not quantified with a standard curve, a relative quantification was performed by dividing the peak area by the internal standard area, represented by the percent column in Table S.9. Table S.9 includes only chemicals that increased in relative response ratio from the pre- to during-disinfection and the pre- to post-disinfection stages.
Table S.9 Non-quantified disinfection by-products for VHP.
Material Chemical Percent
Aged Carpet, LL .alpha.-Methylstyrene 6
Acetophenone 9
Cyclohex-1,4,5-triol-3-one-1-carbo 22
Aged HVAC Duct .alpha.-Methylstyrene 9
Carpet, LL .alpha.-Methylstyrene 8
1-Iodo-2-methylnonane 10
Carpet, T
Carpet, PVC Benzaldehyde 2
Ceiling Tile .alpha.-Methylstyrene 3
1-Hexadecene 7
Phenol, 2,4-di-t-butyl-6-nitro- 4 Concrete Hexadecane,
2,6,10,14-tetramethyl-1-Tetradecene Methane,
iodo-GWB w/ Satin Paint Toluene 4
GWB w/ Flat Paint
GWB w/ Wallpaper Undecane, 3-methyl- 5
n-Hexadecanoic acid 13
1-Hexadecene 4
GWB Backing 1-Hexadecene 5
Phenol, 2,4-di-t-butyl-6-nitro- 5
HVAC Duct Benzaldehyde 1
.alpha.-Methylstyrene 4 Acetophenone 3 Tridecane, 3-methyl- 6 1-Tetradecene 21 3-Tetradecene, (Z)- 42 1-Hexadecene 11 Phenol, 2,4-di-t-butyl-6-nitro- 3 Linoleum 1-Tetradecene 23 1-Hexadecene 62 Linoleum w/ Polish MDF Acetic acid 22
MDF w/Laminate Undecane, 3-methyl- 10
1-Dodecene 15
1-Tetradecene 41
1-Hexadecene 70
Phenol, 2,4-di-t-butyl-6-nitro- 14
Metal File Cabinet 1-Pentadecene 3
Office Partition .alpha.-Methylstyrene 5
Cyclotetrasiloxane, octamethyl 65
Benzothiazole 19
5-Tetradecene, (E)- 4
Cyclohex-1,4,5-triol-3-one-1-carbo 3 Paper Cyclohex-1,4,5-triol-3-one-1-carboxylic 13
Paper w/ Toner
Particle Board Toluene 5
VCT VCT w/ Polish
