Table III.

Pre-contamination methods and summary of results by outcome

Study	Test agent and conditions	Intervention	Mask/component	Findings				Comments
Filtration efficiencya				FE% (absolute difference from control)
Quan et al. [25]	Unneutralized virus aerosol (H1N1 CA/09; 2.5–4 μm volumetric mean diameter) at 17 kPa vacuum	Salt coating	Polypropylene filter	Uncoated: 0.8 3 mg/cm2: 54.3 (+53.6) 11 mg/cm2: 69.0 (+68.2) 19 mg/cm2: 83.9 (+83.1)				Increasing FE observed with increasing salt coating concentrations; P-values not reported for comparisons with control.
Tseng et al. [27]	Unneutralized bacteria aerosol (104 cfu/m3 experiment; 0.5–2.1 μm aerodynamic particle diameter) at 46 L/min flow rate (stated as equivalent to 95 L/min on full mask)	GS5		A. baumannii	E. faecalis	S. aureus	P-value	No significant increase in FE of mask filter layer with GS5 coating.
			Outer layer	60.7 (+6.3)	55 (+12.3)	69.3 (+18.2)	0.005
			Polypropylene filter	99.3 (+1.8)	99.8 (+1.1)	99.9 (+0.6)	NS
			Interior layer	65.4 (+8.9)	59.5 (+10.0)	62.8 (+6.5)	0.02
	Charge-neutralized NaCl aerosol (0.075 μm median particle diameter) at 85 L/min flow rate	GS5	Full mask	77.6 (–1.8), NS				No significant change in FE with GS5 coating.
Li et al. [24]	Aerosolized KCl–fluorescein solution sprayed on to full mask worn by exercising human subjects. Flow rate, particle size and charge not reported.	Nanoparticle emulsion	Outer layer	82.0 (+2.0)				Results presented as percentage of total KCl particles found in each layer, respectively; KCl not reported for subject's face (i.e. cannot determine penetration through mask). P-values not reported for comparisons with control.
			Polypropylene filter	13.0 (–3.0)
			Interior layer	4.5 (+1.5)
Shen et al. [26]	Aerosolized latex microspheres + synthetic blood (average particle size 1.0 μm). Flow rate and particle charge not reported. Each layer tested three times, in three individual masks.	Repellant		Uncoated (0% repellant)	6% repellant	12% repellant	P-value	Results presented as percentage of total particles found on each mask layer respectively in the three masks tested. 0% found in inner layers of all masks, suggesting FE of native mask filter was unchanged by presence of repellent-coated outer layer. Outcome evaluated with laser scanning confocal microscope.
			Outer layer	36.2%	25.8%	27.4%	<0.0001
				37.7%	26.8%	27.4%
				40.6%	29.2%	29.4%
			Polypropylene filter	63.4%	74.2%	72.0%	0.032
				62.2%	73.2%	72.0%	0.043
				55.3%	56.5%	57.2%	NS
			Interior layer	0.0%	0.0%	0.0%	Not reported
				0.0%	0.0%	0.0%
				0.0%	0.0%	0.0%
Airflow resistanceb				Measured variable (absolute difference from control)
Tseng et al. [27]	Applied: flow rate (85 L/min) over full mask	GS5	Full mask	Pressure reduction: 16.8 (+1.0) mmH2O, NS				No significant changes in airflow resistance
Demir et al. [22]	Applied: pressure reduction (12.7 mmH2O) over mask filter piecesc	N-halamine	Polypropylene filter	Flow rate: 26.7 (–0.6) mL/s/cm2, P-values not reported
Li et al. [23]	Applied: pressure reduction (10 mmH2O) over full mask	Nanoparticle emulsion	Full mask	Flow rate: 18.4 (–1.4) mL/s/cm2, NS
Germicidal effect				Pathogen load (log10 reduction)
Quan et al. [25]	Aerosolized influenza virus (strain not reported) with post-inoculation incubation of 5–60 min.	Salt coating	Polypropylene filter	Log10 reduction at 5, 15, 60 min post exposured,e N0 = viral load on untreated filter at 5 min incubation Uncoated: 0.0 (N0), 1.7, 2.0 3 mg/cm2: 2.7, 2.8, BDL, P < 0.001 11 mg/cm2: 2.9, 3.0, BDL, P < 0.001 19 mg/cm2: 3.0, 3.0, BDL, P < 0.001				Good germicidal effect (log10 reduction >3 in pathogen load) after 60 min incubation in all concentrations of salt coating.
Tseng et al. [27]	Aerosolized bacteria (104 cfu/m3 experiment) with post-inoculation incubation of 0 min. N0 = sterile water-coated mask pathogen load immediately post exposure	GS5		Log10 reduction immediately post exposuref				Inadequate germicidal effect (log10 reduction <<3 in pathogen load) on all GS5-coated mask layers.
				A. baumannii	E. faecalis	S. aureus	P-value
			Outer layer	0.8	0.9	0.8	Not reported
			Polypropylene filter	1.0	0.8	0.8	Not reported
			Interior layer	0.8	0.9	0.9	Not reported
Demir et al. [22]	Aerosolized bacteria with post-inoculation incubation of 10 min. N0 = uncoated mask at 10 min post exposure	N-halamine	Polypropylene filter	Log10 reduction at 10 min post exposured				Good germicidal effect (log10 reduction >3 in pathogen load) by 10 min
				S. aureus	E. coli	p-value
				4.4	3.2	Not reported
Li et al. [23]	Bacterial suspensions (105 cfu/mL) with post-inoculation incubation of 0 and 24 h N0 = uncoated mask at 0 h	Nanoparticle emulsion	Outer layer	Log10 reduction at 0, 24 h post exposured				Good germicidal effect (log10 reduction >3 in pathogen load) by 24 h
				S. aureus	E. coli	P-value
				Uncoated: 0.0 (N0), –0.3	Uncoated: 0.0 (N0), 0.1	Not reported
				Nanoparticle-coated: –0.2, 5.7	Nanoparticle-coated: 1.4, 5.9
In-vivo infection prevention				Measured variable
Quan et al. [25]	Aerosolized virus (H1N1 CA/09, H1N1 PR/34, or H5N1 VN/04) 8-week-old female inbred BALB/c mice N0 = lung viral titer (H1N1 CA/09) following aerosolization through uncoated filter	Salt coating	Polypropylene filter	16-day survival (%)				All mice protected by salt-coated filter barriers survived after exposure to lethal dose of aerosolized virus (surrogate mortality endpoint of >25% loss in body weight). Full data across all viruses available only for 11 mg/cm2 salt-coated filter
				H1N1 CA/09	H1N1 PR/34	H5N1 VN/04
				Uncoated: 0% 3 mg/cm2: 100% 11 mg/cm2: 100%	Uncoated: 0% 19 mg/cm2: 100% 11 mg/cm2: 100%	Uncoated: 0% 11 mg/cm2: 100%
				Log10 reduction in lung viral titreg				All surviving mice had reduced, but detectable, lung viral titres.
				Uncoated: 0.0 (N0)
				3 mg/cm2: 0.6, P < 0.005
				11 mg/cm2: 1.1, P < 0.005
				19 mg/cm2: 1.3, P < 0.005

BDL, below detection limit; cfu, colony-forming units; FE, filtration efficiency; GS5, Goldshield 5 quaternary ammonium agent; H1N1 CA/09, H1N1 influenza virus (A/California/04/2009); H1N1 PR/34, H1N1 influenza virus (A/Puerto Rico/08/2934); H5N1 VN/04, H5N1 influenza virus (A/Vietnam/1203/2004); KCl, potassium chloride; N₀, time zero from which log₁₀ reduction factor was calculated; NaCl, sodium chloride; NS, not statistically significant.

^aFE to testing agent used, expressed as a percentage. A higher percentage filtration efficiency indicates better mask performance.

^bAirflow resistance assessed the ‘breathability’ of the mask at tidal breathing. A lower airflow resistance means better breathability.

^cStudy reported pressure reduction and flow rate in inches of water and cubic feet per minute per square foot, respectively. Results converted to SI units.

^dColony-forming units or plaque-forming units reported in study, as applicable. Results converted to log₁₀ reduction factors.

^ePlaque-forming units below detectable limit. Detection limit of assay not reported; log₁₀ reduction factor cannot be calculated.

^fColony-forming unit reduction percentages reported in study. Results converted to log₁₀ reduction factors.

^gAbsolute values for lung viral titres reported in study. Results converted to log₁₀ reduction factors.