Figure 1
World map presenting the investigated cities.
Figure 2
Dedicated outdoor air system (DOAS) configurations for the three operation scenarios: baseline scenario (DOAS with a baseline filtration), optimum scenario (DOAS with an optimal filter grade) and bypass scenario (DOAS with a baseline filter plus a filter bypass).
Table 1
Filter grades, PM2.5 arrestance efficiencies and pressure drops for a ventilation airflow of 0.944 m3/s (during occupied hours).
| FILTER-GRADE EN 779 (CEN 2012) | FILTER-GRADE MERV | PM2.5 ARRESTANCE EFFICIENCY (%) | (Pa) |
|---|---|---|---|
| G4 | MERV 7 | 20% | 70 |
| M5 | MERV 8 | 25% | 80 |
| M6 | MERV 10 | 30% | 97 |
| F7 | MERV 12 | 70% | 150 |
| F8 | MERV 14 | 80% | 203 |
| F9 | MERV 15 | 90% | 264 |
| HEPA | HEPA | 99.7% | 450 |
[i] Note: HEPA = high-efficiency particulate arrestance (filter); MERV = minimum efficiency reporting values.
Table 2
Total PM2.5 arrestance efficiencies and pressure drops for an outdoor air (OA) ventilation airflow of 0.944 m3/s (during occupied hours).
| FILTER-GRADE EN 779 (CEN 2012) | FILTER-GRADE MERV | PM2.5 ARRESTANCE EFFICIENCY (%) | (Pa) |
|---|---|---|---|
| M5 + F7 | MERV 8 + 12 | 77.5% | 230 |
| F7 + F7 | MERV 12 + 12 | 91.0% | 300 |
[i] Note: MERV = minimum efficiency reporting values.
Figure 3
Summary of the inputs to and outputs from the simulation engine’s inputs and outputs.
Figure 4
Representative annual mean outdoor PM2.5 concentrations in the investigated cities.
Figure 5
Outdoor and indoor PM2.5 concentrations in relation to outdoor air classifications (ODA) (EN 16798-3 2017) and corresponding filter grades for baseline scenario (air filtration according to EN 16798-3).
Note: Box plots indicate the minimum, 1st quartile, mean (black cross), median and 3rd quartile, maximum and outlier values. The cross-cutting red line indicates the threshold for the annual mean concentration (10 μg/m3) imposed by WHO (2006) guidelines.
Figure 6
Indoor PM2.5 concentration in relation to outdoor air classifications (ODA) (EN 16798-3 2017) and as the result of the three air filtration scenarios.
Note: Box plots indicate the minimum, 1st quartile, mean (black cross), median and 3rd quartile, maximum and outlier values. The cross-cutting red line indicates the threshold for the annual mean concentration (10 μg/m3) imposed by WHO (2006) guidelines.
Figure 7
Annual energy consumption of the fans to overcome the total pressure drops of the ventilation system as a result of the three different filtration scenarios.
Figure 8
Change of the annual total fan’s energy consumption for the optimum and bypass scenarios relative to the baseline scenario.
Figure 9
Map presenting the duration of time in a year when the filter bypass can be used at each investigated city.
Figure 10
Ratio between average energy savings of the fan and the increase in indoor average PM2.5 levels [(kWh/m2 year)/(μg/m3)] for the optimum and bypass scenarios in each investigated city.
Note: Data in the city of Kampala were partially presented as the ΔE/ΔPM2.5 ratio and cannot be defined for the bypass scenario. The outdoor PM2.5 concentration was never <10 μg/m3, and the bypass was never activated. Hence, both ΔE and ΔPM2.5 were equal to zero.