A systematic review and meta-analysis of indoor bioaerosols in hospitals: The influence of heating, ventilation, and air conditioning

Abstract

Objectives To evaluate (1) the relationship between heating, ventilation, and air conditioning (HVAC) systems and bioaerosol concentrations in hospital rooms, and (2) the effectiveness of laminar air flow (LAF) and high efficiency particulate air (HEPA) according to the indoor bioaerosol concentrations. Methods Databases of Embase, PubMed, Cochrane Library, MEDLINE, and Web of Science were searched from 1st January 2000 to 31st December 2020. Two reviewers independently extracted data and assessed the quality of the studies. The samples obtained from different areas of hospitals were grouped and described statistically. Furthermore, the meta-analysis of LAF and HEPA were performed using random-effects models. The methodological quality of the studies included in the meta-analysis was assessed using the checklist recommended by the Agency for Healthcare Research and Quality. Results The mean CFU/m3 of the conventional HVAC rooms and enhanced HVAC rooms was lower than that of rooms without HVAC systems. Furthermore, the use of the HEPA filter reduced bacteria by 113.13 (95% CI: -197.89, -28.38) CFU/m3 and fungi by 6.53 (95% CI: -10.50, -2.55) CFU/m3. Meanwhile, the indoor bacterial concentration of LAF systems decreased by 40.05 (95% CI: -55.52, -24.58) CFU/m3 compared to that of conventional HVAC systems. Conclusions The HVAC systems in hospitals can effectively remove bioaerosols. Further, the use of HEPA filters is an effective option for areas that are under-ventilated and require additional protection. However, other components of the LAF system other than the HEPA filter are not conducive to removing airborne bacteria and fungi. Limitation of study Although our study analysed the overall trend of indoor bioaerosols, the conclusions cannot be extrapolated to rare, hard-to-culture, and highly pathogenic species, as well as species complexes. These species require specific culture conditions or different sampling requirements. Investigating the effects of HVAC systems on these species via conventional culture counting methods is challenging and further analysis that includes combining molecular identification methods is necessary. Strength of the study Our study was the first meta-analysis to evaluate the effect of HVAC systems on indoor bioaerosols through microbial incubation count. Our study demonstrated that HVAC systems could effectively reduce overall bioaerosol concentrations to maintain better indoor air quality. Moreover, our study provided further evidence that other components of the LAF system other than the HEPA filter are not conducive to removing airborne bacteria and fungi. Practical implication Our research showed that HEPA filters are more effective at removing bioaerosols in HVAC systems than the current LAF system. Therefore, instead of opting for the more costly LAF system, a filter with a higher filtration rate would be a better choice for indoor environments that require higher air quality; this is valuable for operating room construction and maintenance budget allocation.

Evaluation of the Results of a Periodic Environmental Biosecurity Assessment Program on Air Quality in Controlled Environment Rooms of Hospitals

“…This is in agreement with what was found during the PEBAP, although the highest percentages of isolated fungi in the air were non-opportunistic fungi, among the opportunistic fungi, Aspergillus was the most frequent. We found low percentages of opportunistic fungi in comparison to other studies (Alberti et al, 2001; Caggiano et al, 2014), although comparing results is complicated by the diverse methodologies applied, different HVAC system features, and different incubating temperatures (Dai et al, 2021).…”

Relationship Between Airborne Fungi Presence and the Position of the High Efficiency Particulate Air Filter in the Heating, Ventilation, and Air Conditioning System

“…HVAC systems can help control airborne fungi transmission by influencing dilution, exposure time, and airflow patterns. The high-efficiency filtration in HVAC systems reduces airborne infectious particles and prevents the spread of fungal spores (Dai et al, 2021; Hahn et al, 2002; Oren et al, 2001). The samples were recollected in a periodic environmental biosecurity assessment program for validation of controlled environment rooms; these programs are a useful tool that contribute to improving and maintaining indoor environmental conditions (Sabuco-Tébar et al, 2022).…”

“…The high-efficiency filtration in HVAC systems reduces airborne infectious particles and prevents the spread of fungal spores (Dai et al, 2021; Hahn et al, 2002; Oren et al, 2001).…”

“…Heating, Ventilation, and Air Conditioning (HVAC) systems can help reduce the presence of microorganisms in the air and on surfaces in hospital rooms through dilution, pressurization, and adequate filtration processes (Belizario et al, 2021; Dai et al, 2021; Li et al, 2007; Lin et al, 2022; Sabuco-Tébar et al, 2020; Stockwell et al, 2019). UNE 100713 (2005) is the Spanish standard of reference for air conditioning in hospitals.…”

“…This standard establishes three levels of filtration for Class I rooms with very high air cleaning requirements (such as ultraclean operating rooms, conventional operating rooms, sterile material warehouse, and delivery rooms), and it also establishes that the third level of High Efficiency Particulate Air (HEPA) filtration is installed in the air supply unit itself. HEPA filters improve air quality of controlled environment rooms by reducing the entry of microorganisms (Dai et al, 2021; Hahn et al, 2002; Oren et al, 2001); they can remove 99.97% of particles ≥0.3 µm in size, as reference Aspergillus spp. spores are 2.5–3.0 µm in diameter (Sehulster et al, 2003).…”