Dynamic Insulation Systems to Control Airborne Transmission of Viruses in Classrooms: A Review of 'Airhouse' Concept

The discovery of the Covid-19 virus in China at the end of 2019 has drastically altered the global landscape. The virus, which has now become a pandemic, has wrought devastation on the world, infecting over 500 million people and killing over 6 million. The virus's mutation into a few variations, however, has enabled the world's alarming situation to continue until now. Airborne particles and viruses including the new Covid-19 variant -Omricon, is not only extremely contagious but also can be transferred by airborne transmission, putting vulnerable people like children at risk, particularly in classrooms. Amongst the strategies to control airborne transmission of viruses and to improve indoor thermal and air quality is using ventilation strategies -such as dynamic insulation. Thus, this paper will review at how dynamic insulation systems in conventional farming and residential buildings, cleanrooms and other controlled environments work to reduce airborne viruses and particles in a room. An innovative "Airhouse" concept that combines with activated carbon has been researched and investigated with regard to the dynamic insulation systems.This system has a high potential to reduce the air temperature, humidity, and airborne viruses including Covid-19 whilst maintaining a steady airflow rate in a normal room. Therefore, it has a great deal of potential to decrease or eliminate concerns about the transmission of airborne viruses and adapt ventilation systems to new pandemic threats.

Future challenges and their impact on respiratory health and lung cancer

Air pollution, climate and population health are closely related in terms of their impacts on respiratory health and lung cancer. Air pollutants contribute to the exacerbation of chronic respiratory problems such as COPD and asthma. Air pollutants are also toxic and carcinogenic, initiating and promoting lung cancer development. Climate change in relation to environmental pollution affects the geographical distribution of food supply and diseases such as pneumonia in adults and children. The threat of air pollution, and hence global warming and climate changes, and their effects on population and respiratory health, is an imminent threat to the world and deserves immediate and sustainable combating strategies and efforts. The goals are to increase public awareness and engagement in action, with alignment of international collaboration and policy, and with steering towards further research. Now is the prime time for international collaborative efforts on planning and actions to fight air pollution and climate change before it is too late.Copyright © ERS 2021.

Evaluation of a Low-Cost Air Renewal System for Indoor Air Quality Control in a Climate Chamber

There is a growing concern about Indoor Environmental Quality (IEQ) in buildings as humans are spending longer in indoor environments, whether this is associated or not with climate change and vulnerability to extreme weather events. In the wake of the COVID pandemic, the need for indoor air quality control is likely to increase, the result of many adaptations in home environments to switch to remote work. In hot countries in the Global South, one of the alternatives is split A/C units with limited air renewal. While, odorless and colorless CO2, commonly generated by occupants through respiration, is among the relevant indoor air pollutants. The purpose of this study is to evaluate a low-cost, responsive air-renewal system in a climate chamber equipped with a standard split A/C unit. The results show the system's feasibility in curbing IAQ concerns and also highlight the risk of negative impacts on indoor thermal conditions and on energy consumption on using A/C. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

Soft Ionization: Improving Indoor Air Quality

In this paper we report two applications of a subcategory of air cleaning devices based on soft ionization that do not cause molecular fragmentation. A system that includes two unipolar ionizing modules has been used to simultaneously produce positive and negative ions in the air. In one set of experiments a large chamber (28 m3) was used to study the effect of ions on reducing PM1.0 particles produced by a research grade calibrated cigarette. The data presented in this paper were obtained using a carbon-brush-based bipolar ionizer and a MERV 10 filter with electret media in a recirculating HVAC system. Significant improvement in removal rate of fine and ultrafine particles was achieved when using the bipolar ionizer in conjunction with the MERV 10 filter. The second set of experiments were conducted using a 36 m3 chamber, following BSL-3 standards, to study the effect of ions on aerosolized SARS-CoV-2. Results of these investigations reveal the inactivation rate of SARS-CoV-2 are enhanced when ions are introduced in the air;inactivation rates were increased by more than 60%and 90%for ion densities of 10,000/cc and 18,000/cc. IEEE

Barriers to incorporation of indoor environmental quality (IEQ) principles into building designs

PurposeThis research presents a comprehensive review of the literature on the barriers to incorporating indoor environmental quality (IEQ) principles into building designs. The aim was to identify these barriers in the literature and subsume them under broad categories for the development of a framework showing the interrelationships among the barriers.Design/methodology/approachThe research design used a systematic desktop review which comprised of three levels of screening. The first level allowed for a broad selection of papers;the second level of screening was done to limit the results to papers within the construction industry, and the third level of screening limited the documents strictly to the publication period of 2000–2021.FindingsTwenty-four (24) barriers were identified in the literature, including lack of integrated design teams, which ranked the highest in appearance, high initial costs, poor market for IEQ buildings and higher design charges among others. The identified barriers were classified into six (6) categories namely capacity barriers, economic barriers, process-related barriers, cultural barriers, client-related barriers and steering barriers.Practical implicationsThe findings of this study would enable practitioners and policymakers to better understand what is preventing the widespread adoption of IEQ designs in the built environment and devise actionable strategies to overcome them. It adds to the body of knowledge on IEQ research by categorizing the various barriers that prevent the delivery of IEQ projects.Social implicationsThe developed barriers in this research can serve as a useful checklist to future researchers who may want to validate the barriers to IEQ designs in empirical studies and in different settings.Originality/valueThe interconnectivity revealed by the web-like framework allows for an appreciation of the various barriers of IEQ adoption which would help in expanding the current knowledge on IEQ beyond the narrow scope of isolated barriers. The fact that the papers selected in this study are not limited geographically, underscores the wide applicability of the findings in the global construction industry.

The Benefits of Nursing Home Air Purification on COVID-19 Outcomes: A Natural Experiment.

OBJECTIVES: Improving indoor air quality is one potential strategy to reduce the transmission of SARS-CoV-2 in any setting, including nursing homes, where staff and residents have been disproportionately and negatively affected by the COVID-19 pandemic. DESIGN: Single group interrupted time series. SETTING AND PARTICIPANTS: A total of 81 nursing homes in a multifacility corporation in Florida, Georgia, North Carolina, and South Carolina that installed ultraviolet air purification in their existing heating, ventilation, and air conditioning systems between July 27, 2020,k and September 10, 2020. METHODS: We linked data on the date ultraviolet air purification systems were installed with the Nursing Home COVID-19 Public Health File (weekly data reported by nursing homes on the number of residents with COVID-19 and COVID-19 deaths), public data on data on nursing home characteristics, county-level COVID-19 cases/deaths, and outside air temperature. We used an interrupted time series design and ordinary least squares regression to compare trends in weekly COVID-19 cases and deaths before and after installation of ultraviolet air purification systems. We controlled for county-level COVID-19 cases, death, and heat index. RESULTS: Compared with pre-installation, weekly COVID-19 cases per 1000 residents (-1.69; 95% CI, -4.32 to 0.95) and the weekly probability of reporting any COVID-19 case (-0.02; 95% CI, -0.04 to 0.00) declined in the post-installation period. We did not find any difference pre- and post-installation in COVID-19-related mortality (0.00; 95% CI, -0.01 to 0.02). CONCLUSIONS AND IMPLICATIONS: Our findings from this small number of nursing homes in the southern United States demonstrate the potential benefits of air purification in nursing homes on COVID-19 outcomes. Intervening on air quality may have a wide impact without placing significant burden on individuals to modify their behavior. We recommend a stronger, experimental design to estimate the causal effect of installing air purification devices on improving COVID-19 outcomes in nursing homes.

The size distribution of SARS-CoV-2 genetic material in airborne particles sampled in hospital and home care environments occupied by COVID-19 positive subjects.

Characterizing the size distribution of airborne particles carrying SARS-CoV-2 virus is essential for understanding and predicting airborne transmission and spreading of COVID-19 disease in hospitals as well as public and home indoor settings. Nonetheless, few data are currently available on virus-laden particle size distribution. Thus, the aim of this study is reporting the total concentrations and size distributions of SARS-CoV-2- genetic material in airborne particles sampled in hospital and home environments. A nanoMOUDI R122 cascade impactor (TSI, USA) was used to collect size-segregated aerosol down to the sub-micron range in home and in three different hospital environments in presence of infected patients in order to provide the concentration of airborne SARS-CoV-2 genetic material for each particle size range at different sampling locations. Providing one of the largest datasets of detailed size-fractionated airborne SARS-CoV-2 RNA to date, we found that 45.2 % of the total sub- and super-micrometric fractions were positive for SARS-CoV-2 with its genetic material being present in 17.7 % of sub-micrometric (0.18-1 µm) and 81.9 % of super-micrometric (>1 µm) fractions. The highest concentration of SARS-CoV-2 genetic material in total suspended particles (5.6 ± 3.4 RNA copies m-3) was detected in the room occupied with patients with more severe COVID-19 symptoms collected during the patients' high flow nasal oxygen therapy. The highest concentration at certain particle size fraction strongly depends on the sampling environment. However, the contribution of SARS-CoV-2 genetic material was in favour of super-micrometric compared to sub-micrometric particle size range. The evaluation of the individual risk of infection was carried out on the basis of the obtained data considering a hypothetical exposure scenario. The obtained results indicate the necessity of the protective masks in presence of infected subjects, especially while staying for longer period of time in the hospital environments.

New ventilation design criteria for energy sustainability and indoor air quality in a post Covid-19 scenario.

The Covid-19 outbreak raised great attention to the importance of indoor air quality in buildings. Even if the Covid-19 epidemic is nearing an end, all stakeholders agree that increasing outside air flow rates is beneficial for decreasing the likelihood of contagion, lowering the risk of future pandemics, and enhancing the general safety of the interior environment. Indeed, diverse concerns raised about whether the ventilation standards in place are still adequate. In this context, this research intends to assess the suitability of current ventilation standards in addressing the current pandemic scenario and to offer novel criteria and guidelines for the design and operation of HVAC systems, as well as useful guidance for the creation of future ventilation standards in a post-Covid-19 scenario. To that end, a comprehensive analysis of the ANSI/ASHRAE 62.1 is carried out, with an emphasis on its effectiveness in reducing the risk of infection. Furthermore, the efficacy of various ventilation strategies in reducing the likelihood of contagion has been investigated. Finally, because building ventilation is inextricably linked to energy consumption, the energy and economic implications of the proposed enhancements have been assessed. To carry out the described analysis, a novel method was developed that combines Building Energy Modelling (BEM) and virus contagion risk assessment. The analyses conducted produced interesting insights and criteria for ventilation system design and operation, as well as recommendations for the development of future standards.

Effects of various respiratory activities on human aerosol emissions: experimental design and preliminary results

This study combines particle measurements and acoustic measurements to study aerosols generated in breathing, speaking, singing and coughing. Particle measurements are carried out using a portable measurement chamber designed specially for the study. Acoustic measurements of voice production are conduced to standardize measurements in human aerosol emission and to reveal possible reasons for the individual differences in particle generation. Understanding mechanisms of human aerosol generation is important in trying to understand how the airborne transmission of pathogens takes place and furthermore in assessing how to minimize the risk of transmission. The results can be used in the context of all airborne diseases. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Near-field exposure of pathogen-laden respiratory particles based on statistical evaluation of one emitting person indoors

Risk assessment models typically assume ideal mixing, in which the pathogen-laden aerosol particles emitted by a person are evenly distributed in the room. This study points out the local deviation from this idealized assumption and a correlation between the level of pathogen concentration and the distance from the emitter. For this purpose, several numerical studies (CFD) were analyzed, and a validation experiment was performed. Statistical evaluation of the spatial pathogen distribution was used to determine the potential exposure to elevated pathogen concentrations. Compared to an ideally mixed room, at a distance of 1.5 m, the mixing ventilation cases show a 25% risk of being exposed to twice the amount of pathogens and a 5% risk to more than 5 times the assumed value. For displacement ventilation there is a 75% chance of being exposed to less pathogens than in complete mixing at a distance of 1 m. The measurement values agree with the simulation results. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Ventilation solutions for healthcare patient rooms to control respiratory infections

Building ventilation significantly impacts healthy and safe indoor conditions preventing airborne virus spread between people. Therefore, ventilation strategy is a globally essential and health-promoting research topic. Previous studies showed the importance of sufficient ventilation for diluting the virus concentration and reducing the infection risk. The present study investigates the probability of coronavirus infection in the typical room calculated with the Wells Riley proposes recommendations for further research of indoor airflow effect on the virus transmission. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Human exposure against airborne pathogens in an office environment

Airborne exposure has been highlighted during the COVID-19 pandemic as a probable infection route. This experimental study investigates different protection methods at an office workstation, where the concentration characteristics are studied under the mixing ventilation conditions. The protection methods were the room air purifier, personal air purifier, face mask, and workstation partition panels. In experiments, the breathing machine, nebulizer, and syringe pump was used to generate an aerosol distribution of paraffin oil into the room. The breathing thermal manikin and the thermal dummy simulated the exposed and infected person, respectively. The concentration characteristics were measured from the manikin breathing zone. The temporal concentration characteristics were measured from zero concentration to steady-state conditions. The study provides insights into the effects of different protection methods for occupational health and safety decision-making for office indoor environments. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

The effect of ventilation performance on risk of indoor airborne transmission of SARS-CoV-2

Ventilation performance plays a significant role in distributing contaminants and airborne infections indoors. Thus, poorly ventilated public spaces may be at high risk due to the presence of both infectious and susceptible people. Adapting HVAC ventilation systems to mitigate virus transmission requires considering ventilation rate, airflow patterns, air balancing, occupancy, and feature placement. The study aims to identify poorly ventilated spaces where airborne transmission of pathogens such as SARS-CoV-2 could be critical. This study is focused on evaluating the ventilation performance of the building stock and the safety of using the facilities based on measured indoor CO2. The results revealed the spaces with the potential risk of indoor airborne transmission of COVID-19. The study proposes recommendations for utilising air ventilation systems in different use cases. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

COVID-19 airborne transmission risk calculation using CO2 concentrations in a 3D office environment

The ongoing COVID-19 pandemic has caused millions of deaths worldwide along with detrimental socioeconomic consequences. Existing evidence suggests that the rate of indoor transmission is directly linked with the Indoor Air Quality (IAQ) conditions. Most of the existing methodologies for virus transmissibility risk estimation are based on the well-known Wells-Riley equation and assume well-mixed, uniform conditions;so spatiotemporal variations within the indoor space are not captured. In this work, a novel fine-grained methodology for real-time virus transmission risk estimation is developed using a 3D model of a real office room with 31 occupants. CONTAM-CFD0 software is used to compute the airflow vectors and the resulting 3D CO2 concentration map (attributed to the exhalations from the occupants). Simulation results are also provided that demonstrate the efficacy of using CO2 sensors for estimating the infection risk in real-time in the 3D office environment. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

A simple dilution model of the expired jet

Short-range exposure to expired aerosols or droplet nuclei has been considered as the predominant route for SARS-CoV-2. The observed effect of mask wearing, and social distancing suggests the importance of expired jet in the spread of COVID-19. The well-known steady-state dilution model is no longer valid for the interrupted expiratory jet. We reanalysed the existing interrupted jet data and proposed a simple dilution model of expired jet using the two-stage jet model. The interrupted jet consists of two stages, i.e., the jet-like and puff-like stage. Results show dilution factor grows linearly with the distance at the jet-like stage but increases with the cubic of the increasing distance in the puff-like stage. Dilution factor at any distance for the puff-like stage decreases as the activity intensifies, which is still much larger than that estimated via the steady jet model. The findings can be further applied into the short-range airborne exposure assessment. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

The Indoor Air Quality Trilemma: Improving Air Quality, Using Less Energy, and Meeting Stakeholder Requirements

Good indoor air quality (IAQ) is critically important for many aspects of our lives, including as we've found recently in reducing the transmission of airborne diseases such as COVID-19. Delivering good IAQ poses several challenges to organisations: it can require changes in working practices, be bounded by infrastructure capabilities such as buildings and their heating and ventilation systems, and result in substantial energy usage. In this study we have conducted a preliminary investigation measuring IAQ in a typical 'science lab' classroom, and engaging with stakeholders to jointly explore these data. Our mixed methods approach uncovers an indoor air quality 'trilemma', which relates air quality, energy usage, and stakeholder practices that can be mediated by, and understood as, a site for potentially impactful future HCI designs. © 2023 Owner/Author.

Efficiency of UVC radiation as an air disinfectant in a real environment

Microbial contamination of indoor air in public spaces plays an important role in the SARSCoV-2 pandemic. So far, most studies on the reduction of airborne microbial load by UVC irradiation have been conducted as simulations or in laboratory environments. The aim of our study is to demonstrate the efficiency of Upper-Room Ultraviolet Germicidal Irradiation (UVGI) in a real environment like a supermarket. Restrictions on the use of harmful SARSCoV-2 particles for testing in public areas could be circumvented by using airborne germs as indicators. The results of this study show significant germ (bacterial and fungal) reductions by use of UVGI during business hours in a supermarket. Referring to known susceptibility values of airborne germs from previous work, we were able to estimate the effectiveness of the UVGI-system used against corona viruses. It met the requirements for complete disinfection. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

SARS-CoV-2 risk assessment for a 30-minute car journey

In this paper a numerical methodology for close proximity exposure (<2m) is applied to the analysis of aerosol airborne dispersion and SARS-CoV-2 potential infection risk during short journeys in passenger cars. It consists of a three-dimensional transient Eulerian-Lagrangian numerical model coupled with a recently proposed SARS-CoV-2 emission approach, using the open-source software OpenFOAM. The numerical tool, validated by Particle Image Velocimetry (PIV), is applied to the simulation of aerosol droplets emitted by a contagious subject in a car cabin during a 30-minute journey and to the integrated risk assessment for SARS-CoV-2 for the other passengers. The effects of different geometrical and thermo-fluid-dynamic influence parameters are investigated, showing that both the position of the infected subject and the ventilation system design affect the amount of virus inhaled and the highest-risk position inside the passenger compartment. Calculated infection risk, for susceptible passengers in the car, can reach values up to 59%. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

High Time-Resolution Monitoring of Volatile Organic Compounds During Multi-Surface Disinfection Activities in Buildings with PTR-TOF-MS

Increased usage of chemical disinfectants during the COVID-19 pandemic may impact the chemical composition of indoor air in residential and commercial buildings. This study characterized gas-phase concentrations of volatile organic compounds (VOCs) during multi-surface disinfection activities in a tiny house research facility. This unique facility provided a controlled, yet realistic environment for simulating whole-building disinfection events. VOCs were measured in real-time (1 Hz) in the bulk air of the tiny house with a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS). In addition, particle number (PN) size distributions were measured with a high-resolution electrical low-pressure impactor (HR-ELPI+). PTR-TOF-MS measurements demonstrate that chemical disinfectant spray products applied to multiple surfaces can substantially increase indoor VOC concentrations. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

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.