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. 2021 Dec 23;16(12):e0259996. doi: 10.1371/journal.pone.0259996

Table 1. Characteristics of included studies.

Reference Author year Microbiological count type Hospital locations tested Ventilation method ACH Filter type Type of ventilation system
[36] Fu Shaw et al. 2018 BC restricted areas enhanced HVAC system 40 air changes of filtered air per hour HEPA LAF
[33] Hansen et al. 2005 BC restricted areas conventional HVAC system unclear F7 or F9 without LAF
BC restricted areas without HVAC system NA NA NA
BC restricted areas enhanced HVAC system unclear HEPA LAF
[28] Kedjarune et al. 2000 BC inpatient facilities conventional HVAC system unclear unclear unclear
[37] Khawcharoenporn et al. 2013 FC inpatient facilities natural ventilation NA NA NA
FC inpatient facilities natural ventilation NA NA NA
FC inpatient facilities conventional HVAC system unclear unclear unclear
FC inpatient facilities conventional HVAC system unclear unclear unclear
[38] Wan et al. 2011 BC restricted areas enhanced HVAC system 15–23 air changes per hour HEPA LAF
[39] Stocks et al. 2010 BC restricted areas enhanced HVAC system a minimum of 15 exchanges per hour Varicell filter (95% effective at removing particles ≥0.3μm) TAF
[40] Sautour et al. 2009 FC inpatient facilities conventional HVAC system unclear Plasmair™ unclear
[31] Napoli et al. 2012 BC restricted areas enhanced HVAC system unclear HEPA TAF
[41] Perdelli, Sartini et al. 2006 FC inpatient facilities without HVAC system NA NA NA
BC inpatient facilities without HVAC system NA NA NA
FC inpatient facilities conventional HVAC system 6 exchanges per hour minimum efficiency reporting value (80% to 85% efficiency) TAF
BC inpatient facilities conventional HVAC system 6 exchanges per hour minimum efficiency reporting value (80% to 85% efficiency) TAF
FC inpatient facilities enhanced HVAC system 6 exchanges per hour HEPA TAF
BC inpatient facilities enhanced HVAC system 6 exchanges per hour HEPA TAF
[42] Pasquarella et al. 2012 BC restricted areas enhanced HVAC system 15 air changes per hour HEPA unclear
FC restricted areas enhanced HVAC system 15 air changes per hour HEPA unclear
[43] Ortiz et al. 2009 FC restricted areas enhanced HVAC system unclear HEPA unclear
[44] Napoli et al. 2012 BC restricted areas enhanced HVAC system 19.3 air changes per hour HEPA TAF
[45] Landrin et al. 2005 BC restricted areas enhanced HVAC system 30 air changes per hour HEPA unclear
[30] Cristina et al. 2012 BC restricted areas enhanced HVAC system 20 efficacious air exchanges were carried out per hour HEPA TAF
[46] Brun et al. 2013 FC publicly accessible areas conventional HVAC system unclear without HEPA unclear
FC inpatient facilities conventional HVAC system unclear without HEPA unclear
FC inpatient facilities enhanced HVAC system unclear HEPA unclear
[4] Bozic et al. 2019 BC inpatient facilities without HVAC system NA NA NA
FC inpatient facilities without HVAC system NA NA NA
BC inpatient facilities conventional HVAC system unclear unclear unclear
FC inpatient facilities conventional HVAC system unclear unclear unclear
[32] Albertini et al. 2020 BC restricted areas enhanced HVAC system unclear HEPA MAF
BC restricted areas enhanced HVAC system unclear HEPA TAF
FC restricted areas enhanced HVAC system unclear HEPA MAF
FC restricted areas enhanced HVAC system unclear HEPA TAF
[47] Dougall et al. 2019 BC restricted areas enhanced HVAC system unclear HEPA Unclear
[48] Sossai et al. 2011 BC restricted areas conventional HVAC system 12.5 air changes per hour unclear TAF
BC restricted areas enhanced HVAC system 12.5 air changes per hour HEPA additional LAF screen
[49] Cristina et al. 2016 BC restricted areas enhanced HVAC system 19 efficacious air exchanges per hour HEPA TAF
[18] Andersson et al. 2014 BC restricted areas conventional HVAC system unclear F9 displacement ventilation
BC restricted areas enhanced HVAC system unclear HEPA LAF
[50] Perdelli, Cristina et al. 2006 FC restricted areas enhanced HVAC system at least 15 air exchanges per hour HEPA unclear
FC inpatient facilities conventional HVAC system 6 air exchanges per hour filters with 80%-85% efficiency unclear
FC publicly accessible areas conventional HVAC system 2 air exchanges per hour filters with 80%-85% efficiency unclear
[51] Sixt et al. 2007 FC inpatient facilities enhanced HVAC system unclear HEPA LAF
FC inpatient facilities conventional HVAC system unclear PlasmairTM without LAF
FC inpatient facilities without HVAC system NA NA NA
[52] Agodi et al. 2015 BC restricted areas enhanced HVAC system 18 ± 4.5 air changes per hour HEPA LAF
[52] Agodi et al. 2015 BC restricted areas enhanced HVAC system 18 ± 4.5 air changes per hour HEPA MAF
BC restricted areas enhanced HVAC system 18 ± 4.5 air changes per hour HEPA TAF
[21] Alsved et al. 2018 BC restricted areas enhanced HVAC system unclear HEPA turbulent mixed air flow
BC restricted areas enhanced HVAC system unclear HEPA LAF
BC restricted areas enhanced HVAC system unclear HEPA temperature controlled air flow
[53] Cho et al. 2018 FC inpatient facilities conventional HVAC system unclear without HEPA unclear
FC inpatient facilities enhanced HVAC system unclear HEPA unclear
[54] Curtis et al. 2005 FC inpatient facilities conventional HVAC system 2.9 ± 2.7 air changes per hour without HEPA unclear
FC inpatient facilities conventional HVAC system 8.1 ± 7.9 air changes per hour without HEPA unclear
FC inpatient facilities conventional HVAC system 3.8 ± 4.0 air changes per hour without HEPA Unclear
[54] Curtis et al. 2005 FC inpatient facilities enhanced HVAC system 26.6 ± 13.2 air changes per hour HEPA unclear
[55] Dehghani et al. 2018 FC restricted areas enhanced HVAC system unclear HEPA LAF
[56] Kabir et al. 2012 BC inpatient facilities conventional HVAC system unclear unclear unclear
[57] Falvey et al. 2007 FC publicly accessible areas conventional HVAC system unclear 65% filtering efficiency of fan unclear
FC publicly accessible areas conventional HVAC system unclear 65% filtering efficiency of fan unclear
FC publicly accessible areas conventional HVAC system unclear 90–95% filtering efficiency of fan unclear
FC publicly accessible areas conventional HVAC system unclear 90–95% filtering efficiency of fan unclear
FC inpatient facilities conventional HVAC system 3 air exchanges per hour 90–95% filtering efficiency of fan unclear
FC inpatient facilities conventional HVAC system 3 air exchanges per hour 90–95% filtering efficiency of fan unclear
FC inpatient facilities conventional HVAC system 6 air exchanges per hour 90–95% filtering efficiency of fan unclear
FC inpatient facilities conventional HVAC system 6 air exchanges per hour 90–95% filtering efficiency of fan unclear
FC inpatient facilities enhanced HVAC system 12 air exchanges per hour HEPA Unclear
[57] Falvey et al. 2007 FC inpatient facilities enhanced HVAC system 12 air exchanges per hour HEPA Unclear
[58] Friberg et al. 2001 BC restricted areas enhanced HVAC system unclear HEPA LAF

BC, bacterial count; FC, fungal count; NA, not applicable; HEPA, high efficiency particulate air; LAF, laminar air flow; TAF, turbulent air flow; MAF, mixed air flow.