Rapid Review of SARS-CoV-1 and SARS-CoV-2 Viability, Susceptibility to Treatment, and the Disinfection and Reuse of PPE, Particularly Filtering Facepiece Respirators
Abstract
:1. Introduction
2. Methods
Filtering Facepiece Respirators
3. Virus Viability
3.1. SARS-CoV-1
3.2. SARS-CoV-2
4. Disinfection
4.1. Ultraviolet Germicidal Irradiation (UVGI)
4.2. Heat Treatment
4.3. Chemical Disinfection
5. Impact of Disinfection on FFRs
5.1. UVGI
5.2. Heat Treatment
6. Summary of Evidence
6.1. Viability
6.2. Disinfection
6.3. Impact of Disinfection on FFRs
7. Disinfection of Other PPE
8. Proposed Disinfection and Reuse Protocol
- (a)
- Inspection and sorting—careful inspection of PPE (including straps); any soiled and damaged PPE to be discarded, intact PPE to be stored.
- (b)
- Treatment—UVGI, heat, or chemical disinfection, as appropriate.
- (c)
- Re-inspection and sorting—after disinfection, careful re-inspection of PPE (including straps of FFRs) must take place; any PPE with any sign of damage must be discarded; intact PPE to be packaged for reuse, after being appropriately marked as PPE derived from disinfection, including the number of the disinfection cycle.
- (d)
- Fit checking—frontline staff to ensure that FFR passes fit check prior to use, and any disinfected PPE fit properly. At any sign of suboptimal fit, disinfected PPE to be immediately discarded.
9. Cautionary Notes
9.1. Reuse of FFRs
9.2. Extended Use of FFRs
9.3. Ultraviolet Light Toxicity
9.4. Other Pathogens
10. Conclusions
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Database | Results (n) | Search Terms |
---|---|---|
PubMed | 1439 | ((“2003/01/01”[Date-Publication]: “3000”[Date-Publication]) AND (SARS[Title/Abstract]) AND ((steril* [Title/Abstract]) OR (surviv* [Title/Abstract]) OR (viability[Title/Abstract]) OR (N95[Title/Abstract]) OR (PPE[Title/Abstract]) OR (“personal protect*”[Title/Abstract]) OR (disinfect* [Title/Abstract]) OR (decontaminat* [Title/Abstract]) OR (inactivat* [Title/Abstract]) OR (heat[Title/Abstract]) OR (ultraviolet[Title/Abstract]) OR (UV[Title/Abstract])) |
Web of Science ‡ | 1468 | ((TI = SARS) OR (AB = SARS)) AND (TI = (ultraviolet OR UV OR heat OR N95 OR PPE OR “personal protect*” OR surviv* OR viability OR disinfect* OR decontam* OR inactivat*)) OR (AB = (ultraviolet OR UV OR heat OR N95 OR PPE OR “personal protect*” OR surviv* OR disinfect* OR decontam* OR inactivat* OR viability)) |
Google Scholar † | ~182,000 | SARS AND (ultraviolet OR UV OR heat OR inactivation OR inactivate OR decontaminate OR decontamination OR disinfect OR disinfection OR N95 OR PPE OR “personal protective” OR “personal protection” OR survival OR survivorship OR viability) |
Study | Inoculum and Conditions | Materials and Time to Inactivation |
---|---|---|
Duan 2003 [28] | 6 log10 TCID50 in 300 μL Room temperature (~20 °C) LOD not reported | Wood board, mosaic—4 days Glass, press paper, plastic, water, soil—5 days Metal, cloth, filter paper—virus still detected after 5 days Serum, filtrated sputum—4 days Sputum, faeces, filtrated faeces, urine—virus still detected after 5 days |
Bao 2003 [35] | ~6.0–7.5 log10 TCID50 3 temperatures: 4 °C, room temperature (24.5 °C), and 37 °C | 4 °C—~4.0 log10 reduction after 15 days, but no data thereafter Room temperature—~3.5 log10 TCID50 reduction after 5 days, but no data thereafter 37 °C—72 h (~6.0 log10 reduction) |
Li 2003 [29] | Initially 3.0–6.0 log10 TCID50 Inactivation likely <1.0 log10 TCID50 | Cloth—6 h (≥4.0 log10 reduction) Soil—24 h (≥5.0 log10 reduction) Filter paper—48 h (≥3.5 log10 reduction) Wood—48 h (≥2.0 log10 reduction) Stainless steel and glass—48 h (≥5 log10 reduction) Plastic—48 h (≥ 4.7 log10 reduction) |
Lai 2005 [30] | 6.0–6.8 log10 TCID50/mL | Cotton gown, paper—24 h (6.0 log10 reduction) Disposable polypropylene gown—2 days (6.0 log10 reduction) Nasopharyngeal aspirate or throat and nasal swab at room temperature—10 days (~6.0 log10 reduction) Nasopharyngeal aspirate at 4 °C— ~3.8 log10 reduction after 27 days, but no data thereafter |
Rabenau 2005 [31] | 500 μL virus suspension (~6.7 log10 TCID50/mL) applied to dish and left to dry at 21–25 °C, unknown RH LOD = ~1.7 log10 TCID50/mL | Plastic (polystyrene petri dish)—infectivity only lost after 9 days (~5.0 log10 reduction) In suspension (10% FBS) remained infective after 9 days (just ~1.2 log10 reduction), with no data thereafter |
Pagat 2007 [34] | 22 ± 3 °C, 10–25% RH Virus solution (~7.7 log10 TCID50/mL) left to dry on glass petri dish LOD = 1.5 log10 TCID50/mL | Taken 42 days until below LOD (~6.2 log10 reduction) Authors noted that surface decay was much faster in solution than dried samples |
Chan 2011 [32] | 7 log10 TCID50/mL 22–25 °C, 40–50% RH | Plastic well plate—infectivity lost after 21 days in dried form (i.e., 7 log10 reduction) and 28 days in solution. |
Chan 2020 [33] | 7 log10 TCID50/mL 10 μL droplets of virus culture on a glass slide Inactivation ≈6 log10 reduction | 4 °C—only 2 log reduction after 14 days in dried form; <1 log10 loss in solution, but no data thereafter 20–25 °C (RH 63%)—14 days in both forms 33 °C – 3 days in dried form; 5 days in solution 37 °C—3 days in both forms |
van Doremalen 2020 [27] | 3.4–3.7 log10 TCID50/mL 21–23 °C, 40% RH Surface deposits of 50 μL | Cardboard—24 h (~2.1 log10 reduction) Copper—24 h (~1.9 log10 reduction) Stainless steel—3 days (3.1 log10 reduction) Plastic—4 days (2.9 log10 reduction) |
Study | Inoculum and Conditions | Materials and Time to Inactivation |
---|---|---|
Behzadinasab 2020 [36] | ~5.8–6.1 log10 TCID50/mL, 5 μL droplets 22–23 °C, 60–70% RH | Glass—~2.3 log10 reduction after 24 h, but no data thereafter Stainless steel—~1.8 log10 reduction after 24 h, but no data thereafter |
Biryukov 2020 [38] | ~2 log10 TCID50/mL 5 μL droplets LOD = 0.2 log10 TCID50/mL Inactivation ≈1.8 log10 reduction | Stainless steel—inactivation after 24 h at 35 °C and 20%, 40%, and 60% RH; after 48 h at 24 °C and 40% and 60% RH, but not at 20% RH (no data thereafter) Results reportedly similar in acrylonitrile butadiene styrene plastic and nitrile rubber |
Chan 2020 [33] | 6.5 log10 TCID50/mL 10 μL droplets of virus culture on a glass slide Inactivation ≈5 log reduction | 4 °C—only 2 log10 reduction after 14 days in dried form or solution, but no data thereafter 20–25 °C (RH 63%)—5 days in dried form and 14 days in solution 33 °C—3 days in dried both forms 37 °C—24 h in dried form and 3 days in solution |
Chin 2020 [37] | Temperature decay: 6.5 log10 TCID50/mL LOD = 2 log10 TCID50/mL Surface decay at room temperature (22 °C, 65% RH): 4.8–6.1 log10 TCID50/mL 5 μL droplets of virus culture LOD = 2 log10 TCID50/mL | Temperature decay: 4 °C—only 0.7 log10 reduction after 14 days 22 °C—14 days (≥4.5 log10 reduction) 37 °C—2 days (≥4.5 log10 reduction) Room temperature study: Printing paper—3 h (≥2.8 log10 reduction) Tissue paper—3 h (≥3.5 log10 reduction) Cloth—2 days (≥2.8 log10 reduction) Wood—2 days (≥3.7 log10 reduction) Glass—4 days (≥3.8 log10 reduction) Banknote—4 days (≥4.0 log10 reduction) Plastic—7 days (≥4.8 log10 reduction) Stainless steel—7 days (≥4.8 log10 reduction) Surgical mask inner layer—7 days (≥4.8 log10 reduction) Surgical mask outer layer—3.0 log10 reduction after 7 days, but there was remaining infectivity (no data thereafter) |
Fischer 2020 [39] | ~4.5 log10 TCID50/mL 50 μL inoculum on stainless steel and N95 disks 21–23 °C, 40% RH LOD = 0.5 log10 TCID50/mL | N95 respirator—24 h (≥4 log10 reduction) Stainless steel—48 h (≥4 log10 reduction) |
Kasloff 2020 [40] (!) | 1–1.4 cm2 coupons 10 μL droplets ~5.8 log10 TCID50/mL inoculum in soil load (mucin + BSA + tryptone) ~20 °C, 35–40% RH LOD = 0.8 log10 TCID50/mL (inactivation ≈5.0 log10 reduction) | 100% cotton t-shirt fabric—1 day Chemical-resistant nitrile rubber gloves—7 days Nitrile rubber gloves—14 days Stainless steel, plastic face shield, N100 respirator, and polyethylene coveralls—21 days N95 respirator—~4.9 log10 reduction after 21 days, but LOD not reached (no data thereafter) |
van Doremalen 2020 [27] | ~3.2–3.7 log10 TCID50/mL 21–23 °C, 40% RH Surface deposits of 50 μL | Plastic and stainless steel—4 days (3.2 log10 reduction) Cardboard—2 days (~2.0 log10 reduction) Copper—8 h (~1.7 log10 reduction) |
Virus | Study | Inoculum and Conditions | UV Exposure | Key Findings and Notes |
---|---|---|---|---|
SARS-CoV-1 | Duan 2003 [28] | 6 log10 TCID50 in 100 μL culture medium in well plates | 260 nm-length UVC Irradiance: >90 μW/cm2 Distance: 80 cm | Cell culture exposure—undetectable CPE with 300 mJ/cm2 |
Ansaldi 2004 [49] | “standard concentration of cell-grown virus” 1 mL salt solution on a cell culture plate 18 °C, 40% RH | Irradiance: 40 mW/cm2 UV type and distance to light undisclosed | Negative result by cell culture and PCR with 12,000 mJ/cm2 Methods not fully described | |
Darnell 2004 [46] | 2 mL aliquots of virus in well plates ~5.7 log10 TCID50/mL LOD = 1.0 log10 TCID50/mL | UVC 254 nm Irradiance: 4016 μW/cm2 at 3 cm | ~4.6 log10 reduction with ~1450 mJ/cm2 Complete inactivation (≥4.7 log10 reduction) achieved with 3600 mJ/cm2 UVA (365 nm) completely ineffective at a total applied dose of 1920 mJ/cm2 | |
Darnell 2006 [45] | Virus solution in well plates ~5.0 log10 TCID50/mL LOD = 1.0 log10 TCID50/mL | UVC 254 nm Irradiance: 4016 μW/cm2 at 3 cm | Study specific to non-cellular blood products Inactivation in PBS solution (≥4.0 log10 reduction) with 9600 mJ/cm2 Incomplete inactivation in BSA protein solutions with 14,500 mJ/cm2 | |
Kariwa 2006 [50] | 2 mL aliquots open plastic petri dishes 7.6 log10 TCID50/mL LOD = 1.0 log10 TCID50/mL | UV “normal biosafety cabinet UV lights” (likely UVC) Irradiance: 134 μW/cm2 | ~5.3 log10 reduction with 121 mJ/cm2, but LOD not reached with 500 mJ/cm2 (maximum applied dose tested) | |
Heimbuch 2019 [51] | FFR coupons in 3 soiled conditions: no soiling agent artificial saliva (mucin) artificial skin oil (sebum) Controls at 4.6–5.5 log10 TCID50/mL | UVC lamp (254 nm) Distance 15.2–22.9 cm Irradiance: mean 2.3 mW/cm2 | No detectable viable virus in the 3 conditions tested with 1000 mJ/cm2 (i.e., ≥4.0 log10 reduction) | |
Eickmann 2020 [52] | 375 mL platelet concentrates 5.9 log10 TCID50/mL | THERAFLEX UV-Platelets system (UVC 254 nm) up to 200 mJ/cm2 | Below LOD (i.e., ≥3.4 log10 reduction) with 100 mJ/cm2 Note that the system employed achieves virus inactivation more efficiently through vigorous agitation of fluid bags [53] | |
SARS-CoV-2 | Fischer 2020 [39] | ~4.5 log10 TCID50/mL 50 μL inoculum on stainless steel and N95 disks LOD = 0.5 log10 TCID50/mL | UVC 260-285 nm Irradiance 0.55 mW/cm2 at point of exposure | Stainless steel—below LOD (≥4 log10 reduction) with 330 mJ/cm2 N95—LOD not reached with 1980 mJ/cm2 (visually estimated from figure as ~3 log10 reduction), but no data thereafter (i.e., beyond 60 min) |
Heilingloh 2020 [54] | 600 µL 6.7 log10 TCID50/mL in 24 well plates | UVC 254 nm at 1.94 mW/cm2 UVA 365 nm at 0.54 mW/cm2 | UVC achieved >6.7 log10 reduction at 1048 mJ/cm2 UVA achieved 1.0 log10 reduction at 292 mJ/cm2 applied dose | |
Inagaki 2020 [55] | 150 μL with 4.3 log10 plaque forming units (PFU)/mL in 60 mm petri dish LOD = ~1.3 log10 PFU/mL | Deep ultraviolet light-emitting diode (DUV-LED) 280 ±5 nm Irradiance 3.75 mW/cm2 at 20 mm | Below LOD (~3.2 log10 PFU/mL reduction) with 75 mJ/cm2 | |
Smith 2020 [42] | 100 μL of saline/albumin solution with high viral titer “directly infiltrated” into strips from 3 different N95 models, aiming to ‘expose’ the middle layer | UVC 254 nm Applied dose 630 mJ/cm2 to each side (i.e., 1260 mJ/cm2 per sample) | UVC did not inactivate the virus from the N95 samples Authors commented that it would be “hard to imagine a realistic scenario where healthcare workers would face this degree of mask inoculum” | |
Ozog 2020 [56](!) | 10 μL droplet viral stock (≤6.0 log10 TCID50/mL) LOD ≈ 1.8 log10 TCID50/mL, so inactivation up to ~4.2 log10 reduction | UVC 254 nm UVGI device with 4 lamps, irradiance of 16 mW/cm2 at 11.5 cm away Single applied dosed of 1500 mJ/cm2 tested | Four N95 FFR models tested, each with 4 locations tested (nosepiece, apex, chin-piece, and strap), with 3 samples each Most facepiece samples (total n = 32) had viral loads <LOD, but 4 samples from 2 models did not For straps, all samples from 2 models (3 each) were <LOD, but only 1/6 samples were <LOD for other 2 models | |
Ratnesar-Shumate 2020 [57] | 5 μL droplets of viral suspension (‘simulated’ saliva’ or FBS) on stainless steel coupons Virus concentration unspecified but estimated from graphs | UVB 280–315 nm Irradiance 0.16 mW/cm2 for up to 20 min (maximum applied dose 192 mJ/cm2) | ‘Simulated’ saliva: ~2.5 log10 reduction (from ~3 to ~0.5 log10 TCID50/mL) FBS: ~1.1 log10 reduction (from ~2.6 to ~1.5 log10 TCID50/mL) Study aimed to demonstrate SARS-CoV-2 inactivation by sunlight (which does not include the UVC spectrum) |
Virus | Study | Inoculum and Conditions | Heat Treatment Details and Time to Inactivation |
---|---|---|---|
SARS-CoV-1 | Bao 2003 [35] | Initial virus titre 8.0 log10 TCID50 RH not reported | 56 °C—30 min (~8.0 log10 reduction) 70 °C—15 min (~8.0 log10 reduction) However, results showed: 6.5 log10 reduction after 10 min at 56 °C 7.0 log10 reduction after 5 min at 70 °C |
Duan 2003 [28] | 6 log10 TCID50 in 100 μL culture medium in well plates LOD and RH not reported | Inactivation likely ≥4.0 log10 TCID50 56 °C—90 min 67 °C—60 min 75 °C—30 min | |
Darnell 2004 [46] | 320 μL in 1.5 mL polypropylene cryotubes 5–6 log10 TCID50/mL LOD = 1.0 log10 TCID50/mL RH undisclosed | 56 °C—~4.5–5.0 log10 reduction by 20 min, but residual infectivity remained until 90 min (≥5.0 log10 reduction) 65 °C—~4.0 log10 reduction by 5 min, but some infectivity remained until 90 min (≥4.5 log10 reduction) 75 °C—45 min (≥4.3 log10 reduction) | |
Yunoki 2004 [65] | 4.5 to 7.0 log10 TCID50/mL 4 different plasma products spiked with virus Heat treatment “in liquid” (not fully explained) | Virus <LOD after 30 min at 60 °C in: heat-treated/polyethylene glycol-treated intravenous immunoglobulin preparation (~3.0 log10 reduction), haptoglobin preparation (~5.5 log10 reduction), and 25% human serum albumin preparation (~4.5 log10 reduction) Virus in an antithrombin III preparation only inactivated after 60 min at 60 °C (~4.2 log10 reduction) | |
Rabenau 2005 [31] | 500 μL solutions with virus 7.2 log10 TCID50/mL LOD ≈ 1.8 log10 TCID50/mL Unknown RH | 56 °C—30 min (≥5.0 log10 reduction), but this did not happen in presence of protein additive (20% FBS) with ~1.9 log10 reduction after 30 min (no data thereafter) 60 °C—30 min (≥5.0 log10 reduction), regardless of protein additive | |
Darnell 2006 [45] | Samples incubated in heated water bath 4.2–5.2 log10 TCID50/mL LOD = 1.0 log10 TCID50/mL Undisclosed RH | Study specific to non-cellular blood products Human serum—56 °C for 20 min/65 °C for 10 min (~4.2 log10 reduction) Protein solutions—60 °C for 30 min (at highest protein content) (≥3.5 log10 reduction) | |
Kariwa 2006 [50] | Aliquots of virus solution placed in 50 mL tubes Heated in 56 °C water bath 7.4 log10 TCID50/mL | ~5.8 log10 reduction after 5 min at 56 °C Residual activity remained, with complete inactivation after 60 min (≥6.4 log10 reduction) | |
Pagat 2007 [34] | Virus solution (~6.5 log10 TCID50/mL) Heated in water bath LOD = 1.5 log10 TCID50/mL | 58 °C—60 min (≥5.0 log10 reduction) 68 °C—30 min (≥4.7 log10 reduction) | |
SARS-CoV-2 | Auerswald 2020 [66](!) | 140 μL aliquots of the virus (~5.8 log10 TCID50/mL) solution in well plates | 56 °C—30 min (≥5.0 log10 reduction) 98 °C—2 min (≥5.0 log10 reduction) |
Batéjat 2020 [67](!) | ~6.2–6.7 log10 TCID50/mL in 3 media: cell culture, nasopharyngeal samples, and serum LOD = 0.7 log10 TCID50/mL | Cell culture—after 30 min at 56 °C and 15 min at 65 °C (≥5.9 log10 reduction) Nasopharyngeal samples—after 10 min at 65 °C and 3 min at 95 °C (≥5.9 log10 reduction) Serum—after 15 min at 65 °C (≥5.5 log10 reduction) | |
Chan 2020 [33] | 30 μL of virus at 5.5 log10 TCID50/mL + 270 μL of FBS | 3 log10 reduction in virus viability after 30 min at 56 °C Complete inactivation not achieved, but apparently not specifically aimed for | |
Chin 2020 [37] | 5.3–6.7 log10 TCID50/mL in cell culture medium (volume of solution not reported) LOD = 2.0 log10 TCID50/mL | 56 °C—30 min (≥4.6 log10 reduction) 70 °C—5 min (≥3.3 log10 reduction) | |
Daeschler 2020 [68] | 5 μL of virus inoculum at 7.8 log10 TCID50/mL on 1 cm2 coupons from N95 respirators Control samples: 5.2–5.8 log10 TCID50/mL LOD = 2.0 log10 TCID50/mL | 60 min at 70 °C and 0% RH (3.2–3.8 log10 reduction) Effect unchanged with and without a 5 min cool-down period mid cycle | |
Fischer 2020 [39] | ~4.5 log10 TCID50/mL 50 μL inoculum on stainless steel and N95 disks LOD = 0.5 log10 TCID50/mL Dry oven, RH not reported | N95—60 min at 70 °C (≥3.5 log10 reduction) Stainless steel—only 2.0 log10 reduction after 60 min at 70 °C (no data thereafter) | |
Pastorino 2020 [69] | 5 to 6 log10 TCID50/mL in 300 μL aliquots of 3 media: cell supernatant, human nasopharyngeal sample, and human blood serum Dry oven, RH not reported LOD = 0.5 log10 TCID50/mL | Nasopharyngeal sample, blood sera—30 min at 56 °C and 60 min at 60 °C (≥5.0 log10 reduction) Cell supernatant—some samples with inactivation incomplete after 30 min at 56 °C without BSA and after 60 min at 60 °C with BSA (>5.0 log10 but <6.0 log10 reduction). Below LOD after 15 min at 92 °C (≥6.0 log10 reduction). | |
Wang 2020 [70](!) | Unreported volume of virus stocks 7.2 log10 TCID50/mL Heating conditions or RH undisclosed | 37 °C—after 48 h 6.0 log10 reduction but some infectivity remained (no data thereafter) 42 °C—after 24 h 6.0 log10 reduction but some infectivity remained, which disappeared after 48 h 56 °C—30 min (7.0 log10 reduction) 60 °C—15 min (7.0 log10 reduction) |
Study | Treatment Details | FFRs | Key Findings |
---|---|---|---|
Viscusi 2007 [41] | Laminar flow cabinet with a 40 W UVC light (254 nm) Irradiance of 0.24 mW/cm2 Treatment 1: 30 min, total applied dose 400 mJ/cm2 [200 mJ/cm2 per side (i.e., inner and outer)] Treatment 2: 8 hr, total applied dose 6900 mJ/cm2 (3450 mJ/cm2 per side) | 1 unidentified N95 FFR model | Average filter particle penetration not significantly affected by either treatment. No “significant visible changes” observed for any samples after either treatment. |
Viscusi 2009 [77] | Laminar flow cabinet with a 40 W UVC light (254 nm) Average irradiance 0.18 to 0.20 mW/cm2 15 min exposure to each side (outer and inner) Total applied dose ~180 mJ/cm2 per side | Not identified by the authors, but included 3 N95 FFRs and 3 surgical N95 respirators | No effect on filter aerosol penetration, filter airflow resistance, or physical appearance. |
Bergman 2010 [78] | UVC lamp 40 W (254 nm) 45 min exposure at 1.8 mW/cm2 (total applied dose 4900 mJ/cm2) Distance ~25 cm Only the exteriors of the FFRs were exposed | Authors reported using the same equipment as in Viscusi 2009 [77], i.e., 3 N95 FFRs and 3 surgical N95 respirators | UVGI-treated samples had required levels of filter aerosol penetration and filter airflow resistance. UVGI-treated samples had similar mean % penetration to the treated samples tested in Viscusi 2009 [77] at much lower applied doses. There was no observed physical damage to the FFRs. |
Bergman 2011 [79] | Laminar flow cabinet with a 40 W UVC lamp (254 nm) Irradiance of 1.8 mW/cm2 15 min exposure to outer FFR side (total applied dose 1600 mJ/cm2) | 3M 1860, 3M 1870, and Kimberly Clark PFR95-270 | There were no significant changes in FFR fit. There was no observed physical damage to the FFRs. |
Viscusi 2011 [80] | Laminar flow cabinet with a 40 W UVC lamp (254 nm) Irradiance of 1.8 mW/cm2 Total exposure 30 min (15 min inner side and 15 min outer side) Applied dose 1600 mJ/cm2 per side | 3M 8000, 3M 8210, Moldex 2200, 3M 1860, 3M 1870, and Kimberly Clark PFR95-270 | Authors concluded that UVGI unlikely to lead to significant changes in fit, odor detection, comfort, or donning difficulty. One subject stated that a UVGI-treated Moldex 2200 had an intolerable odor afterwards. |
Lore 2012 [81] | Laminar flow cabinet, with dual-bulb 15 W UVC lamp (254 nm), 25 cm above surface Irradiance 1.6 to 2.2 mW/cm2 Maximum total applied dose ~1980 mJ/cm2 over 15 min | 3M 1860s, 3M 1870 | There was no significant decrease in filter performance. |
Lindsley 2015 [82] | UVC (254 nm) 91 × 31 × 64 cm chamber ~27 °C at 25% relative humidity Respirator coupons: 0, 120, 240, 470, 710, or 950 J/cm2 of UVC on each side (one side was exposed at a time) Respirator straps: 0, 590, 1180, or 2360 J/cm2 | 3M 1860, 3M 9210, Gerson 1730, and Kimberly-Clark 46727 | Slight decrease in particle penetration, estimated as up to ~1 percentage point. Small increase in flow resistance (<6% of the original value), independent of applied UV dose. At ≥710 J/cm2 there was major loss of bursting strength for most respirator layers tested, some as much as 90%. For some layers of certain models (3M 9210 and K-C 46727) loss >80% occurred at 470 J/cm2. At 590 J/cm2 the mean strap breaking strengths decreased by 10–21%. The lowest applied dose tested of 120 J/cm2 reduced the bursting strength of the four models tested by 11% to 42% (depending on layer and model). |
Heimbuch 2019 [51] | UVC (254 nm) 10 or 20 cycles of 1000 mJ/cm2, i.e., total applied doses of 10,000 or 20,000 mJ/cm2 per FFR, respectively | 15 models tested 10 cycles–3M 1860, 3M 1870, 3M VFlex 1805, Alpha Protech 695, Gerson 1730, Kimberly-Clark PFR, Moldex 1512, Moldex 1712, Moldex EZ-22, Precept 65-3395, Prestige Ameritech RP88020, Sperian HC-NB095, Sperian HC-NB295, US Safety AD2N95A, and US Safety AD4N95 20 cycles–3M 1860, 3M 1870, 3M VFlex 1805, Kimberly-Clark PFR, Moldex 151 2, and US Safety AD4N95 | Up to 20 cycles of UVGI treatment (20,000 mJ/cm2) did not have a meaningful effect on fit, airflow resistance, or particle penetration for any model tested. Strap strength was unaffected by 10 UVGI cycles, but 20 cycles had some effect on certain models. |
Fischer 2020 [39] | UVC LED lamp (160–285 nm) Up to 3 cycles of 2 h of wear and likely 60 min of UV treatment (estimated applied dose to flat disks 50 cm from light was 1980 mJ/cm2 per 60 min cycle) | 3M 9211+ | Study difficult to interpret as aspects of UV disinfection were insufficiently reported. Negligible effect on filtration performance after 2 cycles (~3960 mJ/cm2), but more marked after 3 cycles, although still within acceptable range. |
Liao 2020 [44] | Sterilizer cabinet 8 W bulb UVC (254 nm) Irradiance not described 10 cycles of 30 min | 15 × 15 cm pieces of meltblown fabric, described as most important N95 FFR layer | The ten 30 min cycles did not affect the fabric’s filtration efficiency. In the absence of information on irradiance, it is not possible to ascertain the actual applied UVC dose. |
Ou 2020 [43] | UVC (200–280 nm) and UVB (280–315 nm) Actual applied dose reaching FFRs unknown; delivered with Xenex LightStrike Germ-Zapping Robots for 5 min within <1 m—authors estimated as >1000 mJ/cm2 | 3M 8210 | There were negligible effects on particle filtration efficiency after 10 cycles (which the authors would have estimated as a total applied UVC dose >10,000 mJ/cm2). |
Ozog 2020 [83] (!) | UVC (254 nm) Each cycle consisted of 1500 mJ/cm2 to the outside-facing surface plus 1500 mJ/cm2 to the wearer-facing surface. | 3M 1860, 3M 8210, 3M 9210, Moldex 1512, and Cardinal Health N95 R/S Respirator | Only fit testing assessed; FFRs had the following number of cycles passed and cumulative UVC doses: 3M 1860—20 cycles, 60,000 mJ/cm2; 3M 9210 and Moldex 1512—2 cycles, 6000 mJ/cm2; 3M 8210 and Cardinal Health—1 cycle, 3000 mJ/cm2. Note that other N95 models failed fit testing before treatment |
Price 2020 [84] (!) | Ten 30 min cycles of UVC (254 nm) in a sterilizer cabinet equipped with 8 W UV light bulb, interspaced with 10 min stand-down periods No quantified information on irradiance or approximate dose | 3M 8200, 3M 8511, 4C AIR KN95, and Jackson R20 | After 10 cycles of UVGI, there was material failure of one model and fit factor reductions of 35% to 96% depending on model. While all models failed after 10 cycles, it is not possible to interpret their results due to complete absence of data on applied dose. However, the respirators were exposed to 5 h of UVC treatment likely equating to very large doses. |
Smith 2020 [42] | UVC (254 nm) 18,400 mJ/cm2 to exterior surface and 4600 mJ/cm2 to interior surface of N95 respirators | 3M 1860, 3M 1870+, and 3M 8511 | There was a reduction in fit scores after UVC treatment across all models, although scores remained within acceptable range for N95 respirators. |
Zhao 2020 [85] | UVC (254 nm from mercury lamps or 265 nm from LED) 1 cycle of either 1000 mJ/cm2 or 10,000 mJ/cm2 | 3M 1860 and Moldex 1500 | Negligible effects on particle filtration efficiency irrespective of dose. Negligible effects on polymer structure, morphology, surface hydrophobicity, or pressure drop and tensile strength of respirator materials, irrespective of applied dose. |
Study | Treatment Details | FFRs | Key Findings |
---|---|---|---|
Viscusi 2007 [41] | Dry heat in laboratory oven Treatment 1: 80 °C for 60 min Treatment 2: 160 °C for 60 min In both, FFRs were turned over at 30 min | 1 unidentified N95 FFR model | At 80 °C, there was a small increase (negligible) in average filter particle penetration. At 80 °C, there were no visible changes after 60 min. At 160° C, FFRs largely melted. |
Viscusi 2009 [77] | Dry heat in laboratory oven Treatment for 1 h at 80, 90, 100, 110, and 120 °C | Not identified by the authors, but included 3 N95 FFRs and 3 surgical N95 respirators | Results are difficult to interpret, but it seems that the models tested maintained their expected aerosol filtration efficiency at 80 °C and 90 °C, without any evident signs of damage. |
Bergman 2010 [78] | 3 cycles of moist heat incubation 30 min incubation at 60 °C, 80% RH in laboratory incubator After 1st incubation, samples were removed from incubator and air-dried overnight. After 2nd and 3rd incubations, samples were removed from incubator and air-dried for 30 min using a fan | Not identified by the authors, but included 3 N95 FFRs and 3 surgical N95 respirators | Heat-treated samples maintained required levels of filter aerosol penetration and filter airflow. Treatment caused all samples of one FFR model to have partial separation of the inner foam nose cushion from the FFR. |
Bergman 2011 [79] | Moist heat incubation 3 cycles, 15 min at 60 °C, 80% RH | 3M 1860, 3M 1870, and Kimberly Clark PFR95-270 | There were no significant changes in FFR fit. 3M 1870 samples experienced a slight separation of the inner foam nose cushion (some to a lesser or greater degree) from the FFR body, but multiple treatments did not appear to increase the level of separation compared to a single treatment. |
Viscusi 2011 [80] | Moist heat incubation 30 min at 60 °C, 80% RH | 3M 8000, 3M 8210, Moldex 2200, 3M 1860, 3M 1870, and Kimberly Clark PFR95–270 | For two models (3M 8210 and Moldex 2200), there was a reduction in fit; for one model (3M 1860), there was a small increase in odor response; but both effects were deemed to be negligible. 3M 1870 samples experienced a slight separation of the inner foam nose cushion (some to a lesser or greater degree) from the FFR body. Authors concluded that moist heat incubation unlikely to lead to significant changes in fit, odor detection, comfort, or donning difficulty. |
Lore 2012 [81] | Moist heat incubation Uncertain temperature, but likely 65 °C for 20 min, unknown RH | 3M 1860s, 3M 1870 | There was no significant decrease in filter performance. |
Anderegg 2020 [92] | Moist heat treatment for 30 min at 85 °C and 60–85% RH (there were additional 10 min at start until temperature and RH reach target levels) | 3M 1860, 3M 1870, 3M 8210 Plus, HKYQ N95, and Chen Heng V9501 KN95 | All FFRs passed particle filtration efficiency testing after 5 heat treatment cycles. All 3M FFRs passed quantitative fit testing after 5 heat treatment cycles. Chen Heng V9501 KN95 and HKYQ N95 FFRs failed fit testing before any treatment. |
Daeschler 2020 [68] | 5, 10, or 15 heat treatment cycles depending on test type Dry heat: 60 min at 70 °C and 0% RH Moist heat: 60 min at 70 °C and 50% RH | 3M 8110s, 3M 9105s, 3M 8210, and 3M 1860s | Microstructural analysis of N95 filter layer (max 10 cycles at 0% and 50% RH)—no effect on diameter of filter fibers. Fit testing (max 15 cycles at 0% and 50% RH)—all FFRs passed tests. Particle filtration efficiency (max 10 cycles at 0% and 50% RH)—all FFRs passed tests. Breathing resistance (max 10 cycles at 0% and 50% RH)—all FFRs passed tests. |
Doshi 2020 [93](!) | Moist heat treatment on a stove: ≥40 min at 65–80 °C and ~40–60% RH | Unknown Kimberly Clark model | Rudimentary testing showing no effect on particle filtration efficiency after 5 cycles. Primary aim of the study seems to have been to demonstrate that is feasible to heat treat N95 FFRs at home using kitchen utensils on a gas stove. |
Fischer 2020 [39] | Dry heat (oven) at 70 °C, unknown RH Up to 3 cycles of 2 h of wear and likely 60 min of treatment | 3M 9211+ | There was a progressive reduction in filtration performance of respirators, which was below acceptable range after 3rd cycle. |
Harskamp 2020 [88] | Autoclave 34 min cycle: 12 min pre-heating, 17 min steam treatment at 121 °C, and 5 min drying Up to 3 cycles | FFP2: 3M 1862+, 3M 9322+, Maco Pharma ZZM002, and San Huei 2920V FFP3: Safe Worker 1016 | 50% of FFP3 respirators were deformed and failed seal checks; all other respirators were intact upon inspection. The 3M 1862+ was the only respirator that continued to perform within the required range after 3 treatment cycles. All other respirators had particle filtering efficiency affected after one treatment cycle, performing below the required range (particularly for smaller particles—0.3 μm), with the magnitude of the reduction in performance varying between models. |
Li 2020 [94] | 20 cycles of 30 s 100 °C steam treatments (inside a steamer) | 3M 1860 | Methods lacking details, and amongst other things, unclear whether there was a cool down period between cycles (due to short duration). Authors concluded that 20 cycles “did not affect fit testing performance”, but few details provided. |
Liao 2020 [44] | Dry heat: up to 50 cycles of 30 min at 75 °C, unknown RH Low RH heat: up to 50 cycles of 20 min at 85 °C and 30% RH Moist heat: up to 20 cycles of 20 min at 85 °C and either 70% or 100% RH Steam treatment: 10 min with water vapor (i.e., ~100 °C) | 15 x 15 cm pieces of meltblown fabric, described as the most important layer of N95 FFRs | Dry heat: no appreciable decrease in filtration efficiency after 50 cycles (i.e., 1500 min). Low RH heat: unaffected filtration efficiency of fabric after 50 cycles (i.e., 1000 min). Moist heat: unaffected filtration efficiency of fabric after 20 cycles (i.e., 400 min). Steam treatment: no change in filtration efficiency after 3 cycles, but drop in efficiency (from ~97% to ~85%) after 5 cycles, explained by the authors as due to loss of static charge of the fibers. |
Liao 2020 [44] | Low RH heat: up to 20 cycles of 20 min at 85 °C and 30% RH Moist heat: up to 20 cycles of 20 min at 85 °C and 100% RH | 3M 8210, 4C Air KN95, ESound KN95, and Onnuripan KF94 | All models tested retained filtration efficiency >95% after 20 treatment cycles (i.e., 400 min). |
Loh 2020 [95](!) | Dry heat at 65 or 86 °C, 34–56 min per cycle (variable) Only 1 treatment cycle per respirator | FFP2–3M 9320+ and 3M 8810 FFP3–3M 9332+, 3M 1863+, 3M 1873V+, 3M 8833, 3M 8835, Alpha S-3V, and Honeywell 5321 | There was a reduction in fit observed for all masks after one cycle, but the rate of reduction was highly variable, and most passed fit testing. Study was not standardized and it is difficult to interpret, but key message was variability between models. Note that one respirator failed the fit testing before any treatment. |
Ou 2020 [43] | Dry heat (oven): 30 min at 77 °C, unknown RH Steam treatment: 30 min with water vapor (i.e., ~100 °C) | 3M 8210 | 10 cycles of dry heat or steam treatment had negligible effects on particle filtration efficiency. Dry heat treatment had no effect on the N95 fit. 5 cycles of steam treatment led to failure in fit testing, with evidence of some effect appearing after just one cycle. |
Price 2020 [84](!) | Dry heat (oven): 30 min at 75 °C 5 cycles, interspaced with 10 min cool-down periods at room temperature | 3M 8200, 3M 8210+, 3M 8511, 4C AIR KN95, and Jackson R20 | 5 cycles of heat treatment had a negligible effect on fit testing performance of all 5 mask models tested. |
Tsai 2020 [22] | Dry heat at 92 °C, unknown RH Moist heat at 92 °C, 85% RH Treatment duration not provided, but context suggests 15 min | One unidentified N95 respirator | Minimal information provided, other than basic data showing no effect on particle filtration efficiency after 4 cycles (each 24 h apart) of either dry or moist heat treatment. |
Xiang 2020 [96] | Dry heat at 70 °C (electric oven), unknown RH Single continuous treatment course of 1, 2, or 3 h | 3M 1860 | No reported change in “shape”; no details provided of fit testing results but authors imply that respirators were largely unaffected after 3 h treatment. Minor reduction in filtration efficiency for bacterial aerosols (from 99% to 97% after 3 h) but still within acceptable range (i.e., ≥95%). |
Yim 2020 [97](!) | Dry heat at 70 °C (oven), unknown RH Single continuous treatment up to 90 min | 3M 1860 and Yomasi KN95 | Yomasi KN95 model had filtration efficiency testing <95% even before testing (~83%). Negligible effects of 90 min at 70 °C on filtration efficiency. |
Heat Treatment Temperature | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|
Cumulative Treatment Time | 60 °C | 65 °C | 70 °C | 75 °C | 77 °C | 80 °C | 85 °C | 90 °C | 92 °C | 100 °C |
10 min | ≈[94] | |||||||||
20 min | ≈[81] | |||||||||
30 min | ≈[80] 1 | ≈[44] | ||||||||
45 min | ≈[79] 1 | |||||||||
50 min | ☼[95] 2 | |||||||||
56 min | ☼[95] (!) | |||||||||
60 min | ☼[41,77] | ☼[77] | ☼[22] 3 ≈[22] 3 | |||||||
90 min | ≈[78] 1 | ☼[97] (!) | ||||||||
120 min | ☼[39] | |||||||||
150 min | ☼[84] | ≈[92] | ||||||||
180 min | ☼[96] | |||||||||
200 min | ≈[93](!) 4 | |||||||||
300 min | ☼[43] | |||||||||
400 min | ☼[44] 5 ≈[44] | |||||||||
600 min | ☼[68](!) ≈[68](!) | |||||||||
1000 min | ☼[44] 5 | |||||||||
1500 min | ☼[44] |
© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
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Derraik, J.G.B.; Anderson, W.A.; Connelly, E.A.; Anderson, Y.C. Rapid Review of SARS-CoV-1 and SARS-CoV-2 Viability, Susceptibility to Treatment, and the Disinfection and Reuse of PPE, Particularly Filtering Facepiece Respirators. Int. J. Environ. Res. Public Health 2020, 17, 6117. https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph17176117
Derraik JGB, Anderson WA, Connelly EA, Anderson YC. Rapid Review of SARS-CoV-1 and SARS-CoV-2 Viability, Susceptibility to Treatment, and the Disinfection and Reuse of PPE, Particularly Filtering Facepiece Respirators. International Journal of Environmental Research and Public Health. 2020; 17(17):6117. https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph17176117
Chicago/Turabian StyleDerraik, José G. B., William A. Anderson, Elizabeth A. Connelly, and Yvonne C. Anderson. 2020. "Rapid Review of SARS-CoV-1 and SARS-CoV-2 Viability, Susceptibility to Treatment, and the Disinfection and Reuse of PPE, Particularly Filtering Facepiece Respirators" International Journal of Environmental Research and Public Health 17, no. 17: 6117. https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph17176117