ABSTRACT
Risk calculators have been utilised to predict the risk of infection from SARS-CoV-2. Inputs include the dimensions of the indoor space, number of infected persons and activity, and inhalation rate of susceptible persons. The compartment model requires an estimate of the Air Changes per Hour (ACH) in the space, as the concentration is changing as a result of the dynamic balance between the generation and removal of exhaled quanta. ACH can be estimated using CO2, engineering drawings, or airflow measurements, but these estimates are often incorrect due to mechanical anomalies and mixing inefficiencies, or in the case of CO2, an absence of continuous occupancy for a sufficient amount of time. SF6 as a tracer gas to establish ACH has been used extensively for many decades to measure air exchange. This approach was utilised to assist a school in managing risk of infection in their facility during an exam period. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
ABSTRACT
The paper contributes to existing research on transmission of infectious diseases in indoor environments, with a focus on the SARS-Co V -2 virus, considered in an environment with a potentially high infectious risk, i.e. a university building. A multi-functional zone with variable occupancy schedules involving both students and staff is used as a case study. A computational fluid dynamics (CFD) model is developed to simulate and analyze three scenarios involving mixed, mechanical, and natural ventilation. Based on the physical and operational configuration of the selected zone, initial results show that mechanical ventilation involves areas of stagnant air (i.e. air velocity is less than 0.1m/s), while reliance on natural ventilation leads to increase in C02 levels. Hence, a mixed mode (natural and mechanical) ventilation is suggested. Then, based on the probability of the presence of (an) infected individual(s), considering the local COVID-19 incidence rate, initial estimates suggest that the Delta variant requires the air change rate (ACH) to be increased more than 1000 times, when compared to the original strain. The paper thus establishes a correlation between the prevalence of a given SARS-Co V -2 variant with the required air change rate, emphasizing the need to factor in not only the presence of infected individual(s), based on the local incidence rate, but also the viral charge of the dominant SARS-Co V -2 variant. The paper argues the need for a better controlled and optimized ventilation to ensure safer indoor environments. © 2022 IEEE.
ABSTRACT
Modular construction methods have been widely used in the civil engineering industry as they provide ease of assembly, convenience of design, and allowing for flexibility in terms of placement. With the increasing number of COVID-19 cases, hospitals’ capacity is decreasing as more intensive care units (ICU) rooms are allocated to those cases. The limited capacity can be overcome by using modular construction to provide field hospitals, to accommodate more patients. This paper adopts transient Lagrangian computational fluid dynamics simulations to investigate the importance of having an appropriate ventilation system in place to achieve containment of contaminants within a modular construction room. The model was validated using the results from the experimental simulation of aerosol in an airconditioned space. The performance of having 10, 20, and 40 air changes per hour (ACH) was examined for a room with a geometry of 6.1 × 2.5 × 3.0 m. It was observed that the rate at which the mouth-generated aerosols were filtered towards the ventilation system (outlet) increased by 137% by increasing the ACH from 10 to 40. Aerosol particles landing on equipment decreased by 25% when the rate was increased to 40 ACH. © 2022, Canadian Society for Civil Engineering.