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 H 2 O 2
Dry Fogging System Advantages of PAA/Dry Fog System No residue/toxic byproducts (H 2 O, O 2, CO 2 ) Effective at low temperature (10 C) Portable (Dry Fog System) Rapid Decontamination Rapid Aeration High soil load tolerance
Dry Fogging System Material compatibility Disadvantages of PAA 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 H 2 O, O 2, CO 2 H 2 O, O 2 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 1. Dry Fogging Up to 75-80% RH. 2. Decontamination 3 Step Process Overnight (~18 hours) for laboratory decons. 3. Aeration Down to <1ppm Hydrogen Peroxide.
DFS: Decontamination Cycle 80 RH % Temp C 60 40 20 0 9:41 AM 10:31 AM 11:21 AM 12:11 PM 1:01 PM 1:51 PM
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 ( 10 6 )
Detection Dräger Polytron 2 w/h 2 O 2 Sensor Dräger Pac III w/h 2 O 2 Sensor Dräger H 2 O 2 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 Microbial agents Initial titre** Exposure Result Vesicular stomatitis virus 5.9 2 hours NG Escherichia coli 6.9 1 hour NG Staphylococcus aureus 6.2 1 hour NG Bacillus atrophaeus spores 5.8 Overnight NG Geobacillus stearothermophilus spores* 6.0 30 min NG * Biological Indicator spore strips, contain no protein soil load ** titres are in LOG 10 NG: No Growth
Dry Fogging Experiments: Setup Simulated lab space Metal framing, polypropylene sheets ~700 ft 3
Dry Fogging Experiments: Setup
CFIA CL4 Lab Decon using DFS
BI Locations
10:00 12:06 14:12 16:18 18:24 20:30 22:36 0:42 2:48 4:54 7:00 9:06 11:12 13:18 15:24 17:30 19:36 21:42 23:48 1:54 4:00 6:06 DFS: Main Lab vs. Autoclave Room 100 90 80 70 60 50 40 30 20 10 0 AUTOCLAVE ROOM TEMPERATURE AUTOCLAVE ROOM RELATIVE-HUMIDITY MAIN LAB RELATIVE-HUMIDITY MAIN LAB TEMPERATURE 100 90 80 70 60 50 40 30 20 10 0
10:00 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 Relative Humidity (%RH) Temperature ( C) DFS: RH & Temp 100 90 80 Relative Humidity Temperature 100 90 80 70 70 60 60 50 40 50 40 30 30 20 10 20 10 0 0
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
10:29 11:50 13:11 14:32 15:53 17:14 18:35 19:56 21:17 22:38 23:59 1:20 2:41 4:02 5:23 6:44 8:05 9:26 (HUMIDITY %) Validation Conditions (RH) 100 90 80 70 60 50 40 30 20 10 0
Validation Plan Control PC (1) No more exposure, only testing (1) PCs (5) Powered on (2) 1 1 Test Pcs (4) Powered off (2) 1 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