Under Pandemic: Assessment of Ventilation in Secondary Schools in The Netherlands

To investigate the sufficiency of ventilation during the COVID-19 pandemic for school children, a field study was conducted in 37 classrooms of 11 Dutch secondary schools between October 2020 and June 2021. All the classrooms were visited twice, before and after a three-month national lockdown, when different measures against COVID-19 were taken by the schools. For each visit, both CO2 concentrations and air temperature were measured during school hours, and detailed information on building/classroom characteristics, occupancy, and COVID-19 measures was collected. Results show that before the lockdown, CO2 concentrations in most classrooms exceeded the threshold levels of the Dutch Fresh Schools guidelines. The significantly lower CO2 concentrations measured after the lockdown, however, were mainly due to the decreased occupancy. Moreover, with windows and doors always being opened on purpose, the performance of different ventilation regimes could not be compared, while such behaviour may also lead to thermal discomfort for school children. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Assessing Indoor Air Quality and Ventilation to Limit Aerosol Dispersion—Literature Review

The COVID-19 pandemic highlighted the importance of indoor air quality (IAQ) and ventilation, which researchers have been warning about for years. During the pandemic, researchers studied several indicators using different approaches to assess IAQ and diverse ventilation systems in indoor spaces. To provide an overview of these indicators and approaches in the case of airborne transmission through aerosols, we conducted a literature review, which covered studies both from before and during the COVID-19 pandemic. We searched online databases for six concepts: aerosol dispersion, ventilation, air quality, schools or offices, indicators, and assessment approaches. The indicators found in the literature can be divided into three categories: dose-, building-, and occupant-related indicators. These indicators can be measured in real physical spaces, in a controlled laboratory, or modeled and analyzed using numerical approaches. Rather than organizing this paper according to these approaches, the assessment methods used are grouped according to the following themes they cover: aerosol dispersion, ventilation, infection risk, design parameters, and human behavior. The first finding of the review is that dose-related indicators are the predominant indicators used in the selected studies, whereas building- and occupant-related indicators are only used in specific studies. Moreover, for a better understanding of airborne transmission, there is a need for a more holistic definition of IAQ indicators. The second finding is that although different design assessment tools and setups are presented in the literature, an optimization tool for a room's design parameters seems to be missing. Finally, to efficiently limit aerosol dispersion in indoor spaces, better coordination between different fields is needed. © 2023 by the authors.

A review on indoor environmental quality in sports facilities: Indoor air quality and ventilation during a pandemic

Because of COVID-19, the indoor environmental quality (IEQ) in sports facilities has been a concern to environmental health practitioners. To develop an overall understanding of the available guidelines and standards and studies performed on IEQ in sports facilities, an extensive literature study was conducted, with the aim of identifying: (1) indicators that are being used to assess IEQ in different sports facilities;(2) indicators that are potentially interesting to be used to assess indoor air, in particular;(3) gaps in knowledge to determine whether sports facilities are safe, healthy and comfortable for people to stay and perform their activities. The outcome indicates that most current standards and previous investigations on IEQ in sports facilities mainly focused on dose-related indicators (such as ventilation rate), while building-related indicators (such as ventilation regime) and occupant-related indicators (such as IEQ preferences) were rarely considered. Little attention is given to the fact that ventilation systems may play an important role in the air quality of the location, and few investigations have been performed on the transmission of SARS-CoV-2. This study recommends more research into both occupant and building-related indicators as well as cross-modal effects between various IEQ factors for developing future standards on sports facilities.

Airborne SARS-CoV-2 in home and hospital environments investigated with a high-powered air sampler.

BACKGROUND: The initial aim was to study the effects of face masks worn by recently infected individuals on the airborne spread of SARS-CoV-2, but findings motivated us to proceed with comparing the presence of SARS-CoV-2 in air samples near infected individuals at home with those near infected intensive care unit (ICU) patients. AIM: To assess the presence of SARS-CoV-2 in the air of homes of infected individuals and in ICU rooms of critically ill patients with COVID-19 who were undergoing different forms of potential aerosol-generating medical procedures. METHODS: A high-volume air sampler method was developed that used a household vacuum cleaner with surgical face masks serving as sample filters. SARS-CoV-2 RNA was harvested from these filters and analysed by polymerase chain reaction. Fog experiments were performed to visualize the airflow around the air sampler. Air samples were acquired in close proximity of infected individuals, with or without wearing face masks, in their homes. Environmental air samples remote from these infected individuals were also obtained, plus samples near patients in the ICU undergoing potential aerosol-generating medical procedures. FINDINGS: Wearing a face mask resulted in a delayed and reduced flow of the fog into the air sampler. Face masks worn by infected individuals were found to contain SARS-CoV-2 RNA in 71% of cases. SARS-CoV-2 was detected in air samples regardless of mask experiments. The proportion of positive air samples was higher in the homes (29/41; 70.7%) than in the ICU (4/17; 23.5%) (P < 0.01). CONCLUSION: SARS-CoV-2 RNA could be detected in air samples by using a vacuum cleaner based air sampler method. Air samples in the home environment of recently infected individuals contained SARS-CoV-2 RNA nearly three times more frequently by comparison with those obtained in ICU rooms during potential aerosol-generating medical procedures.

Testing of outward leakage of different types of masks with a breathing manikin head, ultraviolet light and coloured water mist

Since the outbreak of COVID-19, wearing a mask, voluntary or obligatory, has led to diverse and numerous designs. Guidelines for minimum requirements include tests for visual inspection, strength, filtration, and breathing resistance, but not for the fit of a mask. The fit of a mask was assessed by testing the outward leakage of exhaled breath based on the visualization of coloured mist exhaled by a manikin head. Fourteen masks were selected based on differences in design, such as type of material, shape (cheek wings vs. none), filter type, and the number of layers. Leakage expressed in mean mist percentages (visualized with a camera), patterns of coloured mist left inside the masks, as well as visual fit of the masks on the manikin head, showed that a loose fit mask results in more leakage. Also, combining quantitative with qualitative assessment proved to be complementary. Future tests should be conducted on a range of users, covering the best fit over time as well breathability, use, and comfort. The use of face masks, whatever their characteristics, seem an adequate strategy to reduce the dispersion of potential ‘infected’ aerosols into the space from people, as opposed to not wearing one. © 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

Dismantling myths on the airborne transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2).

The coronavirus disease 2019 (COVID-19) pandemic has caused untold disruption throughout the world. Understanding the mechanisms for transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is key to preventing further spread, but there is confusion over the meaning of 'airborne' whenever transmission is discussed. Scientific ambivalence originates from evidence published many years ago which has generated mythological beliefs that obscure current thinking. This article collates and explores some of the most commonly held dogmas on airborne transmission in order to stimulate revision of the science in the light of current evidence. Six 'myths' are presented, explained and ultimately refuted on the basis of recently published papers and expert opinion from previous work related to similar viruses. There is little doubt that SARS-CoV-2 is transmitted via a range of airborne particle sizes subject to all the usual ventilation parameters and human behaviour. Experts from specialties encompassing aerosol studies, ventilation, engineering, physics, virology and clinical medicine have joined together to produce this review to consolidate the evidence for airborne transmission mechanisms, and offer justification for modern strategies for prevention and control of COVID-19 in health care and the community.