Evaluation of Dry Fogging System for Microbial InactivationEvaluation of Dry Fogging System for...
Transcript of Evaluation of Dry Fogging System for Microbial InactivationEvaluation of Dry Fogging System for...
Evaluation of Dry Fogging System for Microbial Inactivation
Carol Stansfield
Senior Biosafety Officer
Safety & Environmental Services
Canadian Science Centre for Human and Animal Health,
Winnipeg, Manitoba
Objectives
• Dry fog: An Overview
• Preliminary Studies
• Dry fog in a Containment Level 4 laboratory
• Dry fog vs computer
• Conclusions
Dry Fogging System
• Fog particle size: ~7.5
• 1/10 Minncare (Peracetic acid solution, MarCor,
USA)
– 22% Hydrogen peroxide, 4.5% Peracetic acid
Mechanism
• PAA is a strong oxidizer
• Oxidation of microbial cell proteins and enzyme
systems
• Not deactivated by peroxidase, catalases that
break down H2O2
Dry Fogging System
Advantages of PAA/Dry Fog System
• No residue/toxic byproducts (H2O, O2, CO2)
• Effective at low temperature (10°C)
• Portable (Dry Fog System)
• Rapid Decontamination
• Rapid Aeration
• High soil load tolerance
Dry Fogging System
Disadvantages of PAA
• Material compatibility
• Compatibility to electronics?
HCOH, GCD, DFS & VHP
HCOH GCD DFS VHP
Health Risk Carcinogen Non-carcinogen Non-carcinogen Non-carcinogen
Humidity Requirement 65 - 80% 65 - 80% 65 - 80% 10 - 60%
Microbicidal Activity Broad Broad Broad Broad
Neutralization Yes No, scrubbed or vented out No, aerated out No, catalytically destroyed
Real time con. Monitoring None Yes None Yes
By-products Hexamine (powder) Chlorites and chlorates H2O, O2, CO2 H2O, O2
EPA registration No Yes Yes Yes
Compatible to electronics No ? ? Yes
Aeration time Long Shortest Short Long
Cost $ $$$ $$ $$$$
Dry Fogging System (Portable)
Ikeuchi, USA • AKIMist “D” • 1-4 Nozzles • 2.5 - 12 L/hr • $5000 USD • 19L reservoir
Dry Fogging System (Mini)
MarCor, USA • MiniDry Fog System • 1 Nozzle • 500 mL/hr • $5000 USD • 500 mL reservoir
DFS Decontamination Process
3 Step Process
1. Dry Fogging
• Up to 75-80% RH.
2. Decontamination
• Overnight (~18 hours) for laboratory decons.
3. Aeration
• Down to <1ppm Hydrogen Peroxide.
DFS: Decontamination Cycle
0
20
40
60
80
9:41 AM 10:31 AM 11:21 AM 12:11 PM 1:01 PM 1:51 PM
RH % Temp °C
DFS: Process Validation
• Chemical Indicators (CI)
Changes from white to grey or black
Indicates a concentration greater than 1%
• Biological Indicators (BI) Spores of Geobacillus stearothermophilus (≥106)
Detection
• Dräger Polytron 2 w/H2O2
Sensor
• Dräger Pac III w/H2O2 Sensor
• Dräger H2O2 Detection Tubes
• Safe concentration: <1ppm
Small Scale Experiments: Setup
Small Scale Experiments: Setup
Disinfectant Testing: QCT
• Quantitative Carrier Test
Soil load (BSA, Mucin,
Tryptone)
Brushed stainless steel
Dried test inoculum
DFS: Effect of Soil Load
NG 30 min 6.0 Geobacillus stearothermophilus spores*
NG Overnight 5.8 Bacillus atrophaeus spores
NG 1 hour 6.2 Staphylococcus aureus
NG 1 hour 6.9 Escherichia coli
NG 2 hours 5.9 Vesicular stomatitis virus
Result Exposure Initial titre** Microbial agents
* Biological Indicator spore strips, contain no protein soil load
** titres are in LOG10
NG: No Growth
Dry Fogging Experiments: Setup
• Simulated lab space
• Metal framing,
polypropylene sheets
• ~700 ft3
Dry Fogging Experiments: Setup
CFIA CL4 Lab Decon using DFS
BI Locations
DFS: Main Lab vs. Autoclave Room
0
10
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30
40
50
60
70
80
90
100
10
:00
12
:06
14
:12
16
:18
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:24
20
:30
22
:36
0:4
2
2:4
8
4:5
4
7:0
0
9:0
6
11
:12
13
:18
15
:24
17
:30
19
:36
21
:42
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:48
1:5
4
4:0
0
6:0
6
0
10
20
30
40
50
60
70
80
90
100
AUTOCLAVE ROOM TEMPERATURE
AUTOCLAVE ROOM RELATIVE-HUMIDITY
MAIN LAB RELATIVE-HUMIDITY
MAIN LAB TEMPERATURE
DFS: RH & Temp
0
10
20
30
40
50
60
70
80
90
1001
0:0
0
10
:35
11
:10
11
:45
12
:20
12
:55
13
:30
14
:05
14
:40
15
:15
15
:50
16
:25
17
:00
17
:35
18
:10
18
:45
19
:20
19
:55
20
:30
21
:05
21
:40
Re
lati
ve H
um
idit
y (%
RH
)
0
10
20
30
40
50
60
70
80
90
100
Tem
pera
ture
(°C
)
Relative Humidity
Temperature
Results: Failed BIs
What happened?
• The fog failed to rise to ceiling
• Raise fogger arm higher, articulating head fogger
• Heat from lab equipment caused stratification of T
• Higher temp will ↓H, prevent dry fog from contactng surface
• Add fans to circulate air, ↓heat load
• May not have achieved desired RH at ceiling
• Add fans to circulate air
Is Dry Fogging System Compatible to Electronics?
• Test Vehicle: Dell Inspiron 560
Sheet metal Plastic Aluminum Copper
Decon Chamber
Validation Conditions (RH)
0
10
20
30
40
50
60
70
80
90
10010:2
9
11:5
0
13:1
1
14:3
2
15:5
3
17:1
4
18:3
5
19:5
6
21:1
7
22:3
8
23:5
9
1:2
0
2:4
1
4:0
2
5:2
3
6:4
4
8:0
5
9:2
6
(HU
MID
ITY
%)
Validation Plan
PCs (5)
Control
PC (1)
Test Pcs
(4)
Powered on (2)
Powered off (2)
1 1
1 1
No more exposure,
only testing (1)
No more exposure,
only testing (1)
Results • BIs
PC, power on---> BI pass (3/3)
PC, power off---> BI pass (2/3)
• Physical
No visual evidence of corrosion, discoloration
• Functional
No evidence of functional impairment by PC-Doctor
Conclusions:
• Potential use for Dry fog/PAA in decontamination
of high containment laboratories and sensitive
electronics
• PAA able to penetrate soil load
• More validation studies required
Acknowledgements
• Jay Krishnan, Senior Biosafety Officer NML
• Laura Landry, Biosafety Officer NML
• Greg Fey, Containment Services PHAC