Risk assessment of airborne virus transmission in an intensive care unit due to single and sequential coughing.

The virus causing COVID-19 has constantly been mutating into new variants. Some of them are more transmissive and resistant to antibiotics. The current research article aims to examine the airborne transmission of the virus expelled by coughing action in a typical intensive care unit. Both single and sequential coughing actions have been considered to get closer to practical scenarios. The objective is to assess the effectiveness of air change per hour (ACH) on the risk of infection to a healthcare person and how the air change rate influences the dispersion of droplets. Such a study is seldom reported and has significant relevance. A total of four cases were analyzed, of which two were of sequential cough. When the ACH is changed from 6 to 12, the average particle residence time is reduced by ∼7 s. It is found that the risk of infection in the case of sequential cough will be relatively low compared to a single cough if the outlet of the indoor environment is placed above the patient's head. This arrangement also eliminates the requirement of higher ACH, which has significance from an energy conservation perspective.

Role of face masks and ventilation rates in mitigating respiratory disease transmission in ICU.

Indoor environments are major contributing locations where the respiratory virus transmission occurs. Higher air change rate (ACH) values (up to 12) have been recommended in hospital environments to reduce virus transmission. In the present study, the Large Eddy Simulation (LES) data of particle transport in a typical intensive care unit (ICU) is used to calculate the infection risk in close proximity interaction. Three different ACH (6, 9, 12) rates with face masks and one case with a healthy person wearing a face shield are considered. The average resident time of the droplets in the ICU is calculated to find the optimal ACH rate. Of the different types of masks analyzed in the present study, the triple-layer mask has shown the most resistance ([Formula: see text] probability of infection) to the penetration of virus-laden droplets, while the single-layer mask has shown the highest risk of infection (up to [Formula: see text]. The results show that the ACH rate has little effect on close proximity transmission. The ACH 9 case provided optimal value for the particle removal, while the ACH 12 has inferior performance to that of ACH 9. From an energy consumption view, our results recommend not using higher ACH in similar indoor environments. Inside indoor environments, it is advised to wear a three-layer face mask and face shield to reduce the risk of infection.

Droplet fate, efficacy of face mask, and transmission of virus-laden droplets inside a conference room.

The second and third waves of coronavirus disease-2019 (COVID-19) pandemic have hit the world. Even after more than a year, the economy is yet to return to a semblance of normality. The conference/meeting room is one of the critical sections of offices that might be difficult not to use. This study analyzes the distribution of the virus-laden droplets expelled by coughing inside a conference room, the effect of ventilation rates, and their positioning. The efficacy of masks is studied to get quantitative information regarding the residence time of the droplets. The effects of evaporation, turbulent dispersion, and external forces have been considered for calculating the droplets' trajectories. We have analyzed six cases, of which two are with masks. Change in the ventilation rate from four air changes per hour (ACH) to eight resulted in a 9 % increment in the number of droplets entrained in the outlet vent, while their average residence time was reduced by ∼ 8 s . The shift in the vents' location has significantly altered droplets' distribution inside a conference room. It results in ∼ 1.5 % of the injected droplets reaching persons sitting across the table, and a similar indoor environment is not recommended. Wearing a mask in the case of eight ACH has presented the best scenario out of the six cases, with a 6.5 % improvement in the number of droplets entrained in the outlet vent and a 9 s decrease in their average residence time compared to the case without a mask. No droplets have reached persons sitting across the table when the infected person is wearing the mask, which follows that a social distancing of 6 ft with a mask is adequate in indoor environments.