IJERPH, Vol. 19, Pages 16135: Evaluation of an Air Cleaning Device Equipped with Filtration and UV: Comparison of Removal Efficiency on Particulate Matter and Viable Airborne Bacteria in the Inlet and Treated Air

Conceptualization, J.A.K., M.L. and P.L.; methodology, P.L., J.A.K. and R.V.P.; validation, P.L., J.A.K. and R.V.P.; formal analysis, P.L., J.A.K. and R.V.P.; investigation, P.L., N.M., D.W., E.S., M.B., W.B.W., D.L. and B.Y.; resources, J.A.K., N.M., J.J.Z. and B.C.R.; data curation, P.L., N.M., D.W., E.S., M.B., W.B.W., D.L. and B.Y.; writing—original draft preparation, P.L.; writing—review and editing, P.L., J.A.K., R.V.P., N.M., J.J.Z., B.C.R. and W.S.J.; visualization, P.L., J.A.K. and R.V.P.; supervision, J.A.K.; project administration, P.L. and J.A.K.; funding acquisition, J.A.K. and M.L. All authors have read and agreed to the published version of the manuscript.

Figure 1. FastAir prototype for air treatment (top view). Untreated air enters on both sides and is filtered and irradiated by UV-C lamps. The air blower facilitates untreated air suction and ejection on treated air.

Figure 1. FastAir prototype for air treatment (top view). Untreated air enters on both sides and is filtered and irradiated by UV-C lamps. The air blower facilitates untreated air suction and ejection on treated air.

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Figure 2. (A): Front view of the upgraded FastAir prototype with UV-C lamps enclosed and a controller box attached above the air outlet. (B): Side view of the upgraded FastAir prototype. MERV-8 filters can be seen at the air inlet. (C): After MERV-8 filters were removed, MERV-13 filters can be seen as the second filtration layer. Aluminum mesh filters follow MERV-13 filters to protect MERV filters from degradation caused by long-term UV irradiation. (D): Eight UV-C light bulbs were installed on each side of the FastAir prototype. Each light fixture supported twin UV-C light bulbs. The air blower can be seen downstream from the UV-C lamp. The gradient of the air flow arrows signifies progressively cleaner air (from (BD)).

Figure 2. (A): Front view of the upgraded FastAir prototype with UV-C lamps enclosed and a controller box attached above the air outlet. (B): Side view of the upgraded FastAir prototype. MERV-8 filters can be seen at the air inlet. (C): After MERV-8 filters were removed, MERV-13 filters can be seen as the second filtration layer. Aluminum mesh filters follow MERV-13 filters to protect MERV filters from degradation caused by long-term UV irradiation. (D): Eight UV-C light bulbs were installed on each side of the FastAir prototype. Each light fixture supported twin UV-C light bulbs. The air blower can be seen downstream from the UV-C lamp. The gradient of the air flow arrows signifies progressively cleaner air (from (BD)).

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Figure 3. The schematic of UV irradiation inside the FastAir prototype. The filtered air entered three UV treatment zones, A, B, and C (upstream from lamps, in the near vicinity of lamps, and downstream of lamps).

Figure 3. The schematic of UV irradiation inside the FastAir prototype. The filtered air entered three UV treatment zones, A, B, and C (upstream from lamps, in the near vicinity of lamps, and downstream of lamps).

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Figure 4. Details of FastAir prototype for air treatment (one symmetrical side shown) following the air flow direction. Treated air can be sampled after each treatment phase (e.g., filtration and UV) for PM and viable airborne bacteria. The red arrow indicates the air sampling location for the inlet (room air), and the green arrows indicate two air sampling locations for different configuration options: (a.) after “filtration only”, (b.) after “UV” or after “filtration + UV”.

Figure 4. Details of FastAir prototype for air treatment (one symmetrical side shown) following the air flow direction. Treated air can be sampled after each treatment phase (e.g., filtration and UV) for PM and viable airborne bacteria. The red arrow indicates the air sampling location for the inlet (room air), and the green arrows indicate two air sampling locations for different configuration options: (a.) after “filtration only”, (b.) after “UV” or after “filtration + UV”.

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Figure 5. Six air cleaning configuration options were used for testing of FastAir prototype in high (top three panels) and low (bottom three panels) air flow rate modes, with both modes having filtration + UV, filtration only, and UV only options. Red and green arrows signify the sampling locations of the inlet and exhaust (treated) air, respectively, for PM and viable airborne bacteria. Each of the six configuration options was tested three (n = 3) times in experimental trials.

Figure 5. Six air cleaning configuration options were used for testing of FastAir prototype in high (top three panels) and low (bottom three panels) air flow rate modes, with both modes having filtration + UV, filtration only, and UV only options. Red and green arrows signify the sampling locations of the inlet and exhaust (treated) air, respectively, for PM and viable airborne bacteria. Each of the six configuration options was tested three (n = 3) times in experimental trials.

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Figure 6. The experimental setup for collecting viable airborne bacteria and PM at a teaching room that housed ~150 laying hens at ISU Poultry Teaching and Research Facility. The red cart was used to deploy the FastAir prototype into the testing room. The brown cart (behind) held all sampling equipment (vacuum pumps, manifolds, and BioSamplers®).

Figure 6. The experimental setup for collecting viable airborne bacteria and PM at a teaching room that housed ~150 laying hens at ISU Poultry Teaching and Research Facility. The red cart was used to deploy the FastAir prototype into the testing room. The brown cart (behind) held all sampling equipment (vacuum pumps, manifolds, and BioSamplers®).

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Table 1. Summary of air flow rate (converted to standard air flow rate) of the FastAir device under different conditions. Bold values refer to the conditions that test the performance of the entire prototype.

Table 1. Summary of air flow rate (converted to standard air flow rate) of the FastAir device under different conditions. Bold values refer to the conditions that test the performance of the entire prototype.

PrototypeFlow Rate ModeConditions (Load)Standard Air Flow Rate *m3/sCFM **OriginalHigh No filters1.282704MERV 13 only1.082280MERV 8 & 131.012146Low No filters0.861813MERV 13 only0.611283MERV 8 & 130.571200Upgraded with UVHigh UV light only1.202537UV light + Al mesh1.162440UV light + Al mesh + MERV 131.022154UV light + Al mesh + MERV 8 & 131.002101Low UV light only0.531115UV light + Al mesh0.511076UV light + Al mesh + MERV 130.491037UV light + Al mesh + MERV 8 & 130.491027

Table 2. Summary of the removal of viable airborne bacteria from the air. The performance metric is the percent reduction defined as the relative difference between inlet and treated concentrations under different configuration options. The percentage is the average of three or four trials conducted for each configuration. The loading of average airborne bacteria concentrations in the inlet air of each trial varied from 444 CFU/m3 to 7378 CFU/m3.

Table 2. Summary of the removal of viable airborne bacteria from the air. The performance metric is the percent reduction defined as the relative difference between inlet and treated concentrations under different configuration options. The percentage is the average of three or four trials conducted for each configuration. The loading of average airborne bacteria concentrations in the inlet air of each trial varied from 444 CFU/m3 to 7378 CFU/m3.

Configuration OptionMean Percentage Mitigation of Airborne Bacteria
Concentrations ± SD *H-F + UV100%H-F100%H-UV79% ± 5%L-F + UV99% ± 2%L-F98% ± 3%L-UV95% ± 5%

Table 3. The mean percentage mitigation of PM concentrations between the inlet and treated air under different configuration options. The performance metric is the percent reduction defined as the relative difference between inlet and treated concentrations under different configuration options. The percentage is the average of three or four trials conducted for each configuration. The loading of average TSP in the inlet air of each trial varied from 97 µg/m3 to 230 µg/m3.

Table 3. The mean percentage mitigation of PM concentrations between the inlet and treated air under different configuration options. The performance metric is the percent reduction defined as the relative difference between inlet and treated concentrations under different configuration options. The percentage is the average of three or four trials conducted for each configuration. The loading of average TSP in the inlet air of each trial varied from 97 µg/m3 to 230 µg/m3.

Configuration OptionMean Percentage of PM Removed (%R) ± SD *TSPPM10PM4PM2.5PM1H-F + UV95% ± 2%85% ± 5%78% ± 7%77% ± 8%76% ± 8%H-F97% ± **%91% ± 1%87% ± 3%87% ± 3%86% ± 3%H-UV50% ± 25%27% ± 24%27% ± 17%30% ± 19%30% ± 19%L-F + UV97% ± 3%91% ± 6%87% ± 8%87% ± 9%88% ± 9%L-F100% ± **%100% ± **%100% ± **%100% ± **%100% ± **%L-UV46% ± 5%11% ± 2%6% ± 2%7% ± 2%7% ± 1%

Table 4. The percentage removal of viable airborne bacteria is normalized by different PM sizes.

Table 4. The percentage removal of viable airborne bacteria is normalized by different PM sizes.

Configuration OptionsNormalized Percentage of Airborne Bacteria Mitigation (%R)by TSPby PM10by PM4by PM2.5by PM1H-F + UV100%100%100%100%100%H-F100%100%100%100%100%H-UV54% ± 9%71% ± 2%71% ± 1%70% ± 1%70% ± 1%L-F + UV68% ± 56%90% ± 17%93% ± 12%94% ± 11%94% ± 11%L-FN/A *N/AN/AN/AN/AL-UV91% ± 7%94% ± 4%95% ± 4%95% ± 4%94% ± 4%p-Values0.01710.00050.00030.00030.0006

Table 5. Summary of UV dose estimations based on the three methods.

Table 5. Summary of UV dose estimations based on the three methods.

UV DoseMethod 1Method 2Method 32-D (mJ/cm2)3-D (mJ/cm3)2-D (mJ/cm2)3-D (mJ/cm3)2-D (mJ/cm2)3-D (mJ/cm3)Flow Rate ModeHigh6.30.451.50.221.40.22Low12.80.923.10.112.90.11

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