Affordable measures to monitor and alarm nosocomial SARS‐CoV‐2 infection due to poor ventilation

Abstract

Since the coronavirus disease 2019 (COVID‐19) outbreak, the nosocomial infection rate worldwide has been reported high. It is urgent to figure out an affordable way to monitor and alarm nosocomial infection. Carbon dioxide (CO2) concentration can reflect the ventilation performance and crowdedness, so CO2 sensors were placed in Beijing Tsinghua Changgung Hospital's fever clinic and emergency department where the nosocomial infection risk was high. Patients’ medical records were extracted to figure out their timelines and whereabouts. Based on these, site‐specific CO2 concentration thresholds were calculated by the dilution equation and sites’ risk ratios were determined to evaluate ventilation performance. CO2 concentration successfully revealed that the expiratory tracer was poorly diluted in the mechanically ventilated inner spaces, compared to naturally ventilated outer spaces, among all of the monitoring sites that COVID‐19 patients visited. Sufficient ventilation, personal protection, and disinfection measures led to no nosocomial infection in this hospital. The actual outdoor airflow rate per person (Qc) during the COVID‐19 patients’ presence was estimated for reference using equilibrium analysis. During the stay of single COVID‐19 patient wearing a mask, the minimum Qc value was 15–18 L/(s·person). When the patient was given throat swab sampling, the minimum Qc value was 21 L/(s·person). The Qc value reached 36–42 L/(s·person) thanks to window‐inducted natural ventilation, when two COVID‐19 patients wearing masks shared the same space with other patients or healthcare workers. The CO2 concentration monitoring system proved to be effective in assessing nosocomial infection risk by reflecting real‐time dilution of patients’ exhalation.

Study on acquired infection of patients in waiting space of fever clinic

“…By controlling the interpersonal distance, the theoretical upper limit of the patient waiting area can be calculated. For waiting space, N=int[A/d 2 ], where int [A/d 2 ] indicates that the calculation result is rounded down and d is the recommended interpersonal distance, which is 1.5m [12] . See Table 1 for the upper limit of capacity in each region.…”

Elucidating the role of environmental management of forests, air quality, solid waste and wastewater on the dissemination of SARS-CoV-2

“…CO 2 levels represent quality of ventilation and may therefore determine SARS-CoV-2 risk levels ( Lu et al, 2021 ; Meiss et al, 2021a ; Peng and Jimenez, 2021 ). Hence, determination of safe indoor CO 2 levels is recommended and could be maintained to less than 700 ppm or close to outdoor levels of less than 450 ppm ( Ahlawat et al, 2020 ; Di Gilio et al 2021 ; Eykelbosh, 2021 ; Lu et al, 2021 ). CO 2 monitors have been suggested to be placed near windows or 2 metres away from individuals and open flames ( Eykelbosh, 2021 ).…”

Teaching Instrumental Analysis during the Pandemic: Application of Handheld CO2 Monitors to Explore COVID-19 Transmission Risks

“…Instead, it has been shown that carbon dioxide (CO 2 ) can be a useful proxy for exhaled human breath and thus relative exposure risk in indoor environments. 23 − 25 There are limitations with this approach for students to consider: other sources of CO 2 exist, and masks and filters reduce exposure to aerosol 26 − 28 but not CO 2 .…”