Experimental study on the control effect of different ventilation systems on fine particles in a simulated hospital ward

Abstract

In recent years, a large number of respiratory infectious diseases (especially COVID-19) have broken out worldwide. Respiratory infectious viruses may be released in the air, resulting in cross-infection between patients and medical workers. Indoor ventilation systems can be adjusted to affect fine particles containing viruses. This study was aimed at performing a series of experiments to evaluate the ventilation performance and assess the exposure of healthcare workers (HW) to virus-laden particles released by patients in a confined experimental chamber. In a typical ward setting, four categories (top supply and exhaust, side supply and exhaust) were evaluated, encompassing 16 different air distribution patterns. The maximum reduction in the cumulative exposure level for HW was 70.8% in ventilation strategy D (upper diffusers on the sidewall supply and lower diffusers on the same sidewall return). The minimum value of the cumulative exposure level for a patient close to the source of the contamination pertained to Strategy E (upper diffusers on the sidewall supply and lower diffusers on the opposite sidewall return). Lateral ventilation strategies can provide significant guidance for ward operation to minimizing the airborne virus contamination. This study can provide a reference for sustainable buildings to construct a healthy indoor environment.

Keywords: Cross-infection; Exposure control; Particulate matter; Side return air distribution; Ventilation performance.

Fig. 1

(a) Front view of the chamber. The white and blue mannequin simulate a healthcare worker (HW) and patient (P) as the source of pollution, respectively. (b) Right side view of the chamber. The figures on the left and right represent a schematic and actual image, respectively.

Fig. 2

Sixteen ventilation systems (White and blue dummies simulate HW and P as the source of the pollution, respectively.) (The green and red arrows indicate the air input and output, respectively.)

Fig. 3

Equidistant view of a simulated multi-P room in the test room, showing the distance between beds and the measurement points for P's respiratory area at a location close to (CD) and far from (FD) the source of the pollution. (a) Schematic (The pink and blue dummies mimic the P as the source of the pollution and an infected P.) (b) Real image.

Fig. 4

The location of the temperature measurement points. (a) Schematic of the right side view; (b) Real image, showing only a few measurement points.

Fig. 5

Location of the air velocity measurement point. (a) Schematic of the front view; (b) Real image, showing only a few measurement points.

Fig. 6

A-G and H velocity clouds. In A-G, the black dotted line frame represents the hospital bed, indicating the location of the hospital bed; the black solid line frame represents the sidewall air outlet, indicating the location of the air outlet. H is a two-dimensional figure, which shows the length, width and height of H after simplifying the experimental chamber.

Fig. 7

(a) The draught rate (DR) under the operation of 16 ventilation systems in a plane with a height of 0.7 m; (b) DR under operating conditions of 16 ventilation systems in a plane with a height of 1.6 m. The figure shows the median line, mean value, general average of all the data at this height, and outliers.

Fig. 8

The k values under seven ventilation system conditions (Strategies A-G). Measurement points: respiratory areas of P and HW and the indoor center point (IC).

Fig. 9

Variation in the particle concentration in the (a) HW respiratory zone; (b) CD respiratory zone; (c) FD respiratory zone.

Fig. 10

The reduced exposure rate (%) under different ventilation modes.

Fig. 11

The cumulative exposure level of the number of particles measured (1.0 E+06 #/m³).

Fig. 12

(a) The PM_2.5 mass concentrations (μg/m³) of HW and IC (the interior center point); (b) PM_2.5 mass concentration (μg/m³) of CD and FD.