Experience with HEPA-filtered Air Purifiers during the COVID-19 Outbreak

Abstract

Ventilation is one of the most important infection control measures against COVID-19. It is divided into natural and mechanical ventilation. In hospital settings, mechanical ventilation is predominant, and it is essential to verify that the mechanical systems are functioning adequately. However, in older buildings, confirming this can be challenging. Recent experimental studies have revealed that air purifiers reduce the incidence of severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) indoors, and their effectiveness in preventing horizontal transmission is promising. Since the emergence of the Omicron strain, our hospital has experienced multiple patients with COVID-19, which has caused revenue losses of tens of millions of yen to the health system, including suspending new admissions and surgical restrictions. Although addressing ventilation systems at the facility level is a fundamental approach, renovations often incur substantial costs and time, making urgent responses difficult. As a temporary measure until our ventilation system was normalized, we installed high-efficiency particulate air (HEPA) -filtered air purifiers in each patient room of one ward in September 2022. Following installation, from late January to February 2023, several patients were diagnosed with symptomatic COVID-19; however, SARS-CoV-2 was detected in the HEPA filters of rooms with patients with asymptomatic COVID-19. This finding indicates that HEPA purifiers may decrease the risk of SARS-CoV-2 in a clinical setting. This report describes the experience of air purifiers with HEPA filters in clinical settings.