Assessment of air handling unit to improve ventilation in congregate living settings: a multicenter cross-sectional study

BACKGROUND: Heating, ventilation, and air conditioning (HVAC) systems can modulate the risk of respiratory virus transmission. In congregate living settings (CLS), variability in the quality of this infrastructure presents an improvement opportunity. METHODS: We performed a cross-sectional study of the air handling units (AHU) of HVAC systems across a network of CLS to identify the most common problems and specific opportunities to improve ventilation. A third-party expert performed systematic HVAC assessments, which were analyzed based on presence and function of key AHU components to determine their association with air changes per hour (ACH) using a multivariable linear regression model. RESULTS: Across 15 participating CLS, the median ACH was 3.3 (IQR = 10.4) in common areas, 3.5 (IQR = 12.6) in resident rooms, and 6.6 (IQR = 9.7) in resident bathrooms. Closed outside air dampers and fans turned off was associated with decreased ACH in resident rooms (-9.5 ACH, 95% CI, -0.2 to -18.9) and resident washrooms (-7.0 ACH, 95% CI, -1.3 to -12.7). The absence of ducted air source was associated with decreased ACH in resident rooms (-12.2 ACH, 95% CI, -1.0 to -23.5). CONCLUSIONS: Across 15 CLS, we identified readily actionable targets for improvements to ventilation. Based on our findings, we propose assessment criteria to optimize the performance of existing AHU. Prospective studies evaluating the impact of a standardized approach to improving AHU on safety of CLS residents are needed.