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.

Towards improved thermal comfort predictions and higher energy savings: building energy model of an open-plan office based on indoor CO2 and temperature controls

In recent work, a Hierarchical Bayesian model was developed to predict occupants' thermal comfort as a function of thermal indoor environmental conditions and indoor CO2 concentrations. The model was trained on two large IEQ field datasets consisting of physical and subjective measurements of IEQ collected from over 900 workstations in 14 buildings across Canada and the US. Posterior results revealed that including measurements of CO2 in thermal comfort modelling credibly increases the prediction accuracy of thermal comfort and in a manner that can support future thermal comfort prediction. In this paper, the predictive model of thermal comfort is integrated into a building energy model (BEM) that simulates an open-concept mechanically-ventilated office space located in Vancouver. The model predicts occupants' thermal satisfaction and heating energy consumption as a function of setpoint thermal conditions and indoor CO2 concentrations such that, for the same thermal comfort level, higher air changes per hour can be achieved by pumping a higher amount of less-conditioned fresh air. The results show that it is possible to reduce the energy demand of increasing fresh air ventilation rates in winter by decreasing indoor air temperature setpoints in a way that does not affect perceived thermal satisfaction. This paper presents a solution for building managers that have been under pressure to increase current ventilation rates during the COVID-19 pandemic. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Under what circumstances would airborne transmission of SARS-CoV-2 occur?

To find out the circumstances under which airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) would happen, we conducted mechanistic and systematic modelling of two Coronavirus disease 2019 (COVID-19) outbreaks, i.e., Hunan 2-bus outbreak and Luk Chuen House outbreak (the horizontal cluster). Computational fluid dynamics (CFD) simulations, multi-zone airflow modelling, multi-route mechanistic modelling, and dose-response estimation were carried out selectively according to the transmission characteristics in each outbreak. Our results revealed that poorly ventilated bus indoor environments bred the Hunan 2-bus outbreak in which airborne transmission predominates;prevailing easterly background wind and probable door opening behaviour led to the secondary infections across the corridor in Luk Chuen House outbreak. Measures to facilitate sufficient ventilation indoors and positive pressure in the housing building corridor may help minimise infection risk. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Template for Extended Abstract contributions to INDOOR AIR 2022

This investigation presents results of Computational Fluid Dynamics (CFD) modelling of aerosol behaviour within an arbitrary 'realistic' 100m2 office environment, with dynamic and variable respiratory droplet release profile applied based on published findings (Morawska et al., 2009). A multitude of ventilation strategies and configurations have been applied to the base model to compare the effectiveness of reducing the concentration of suspended aerosols over time. A key finding of the investigation indicates a relatively low sensitivity to increasing outside air percentage, and that the benefit from this strategy is heavily dependent on the in-duct droplet decay factor. The application of local recirculating air filtration systems with MERV-13 filters mounted on occupant desks proved significantly more effectiveness than increasing outside air concentration from 25% to 100% in reducing the quantity of suspended aerosols. This highlights that the ventilation industry should perhaps focus on opportunities to integrate filtration systems into furniture, partitions, cabinetry etc., and that an appliance-based solution may be more beneficial for reducing COVID-19 transmission in buildings (and likely more straightforward) than modifications to central ventilation systems, particularly in the application of refurbishments and retrofits. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Air quality changes in Shijiazhuang during COVID-19 outbreak

[Background] The coronavirus disease 2019 (COVID-19) was first detected in December 2019. To combat the disease, a series of strict measures were adopted across the country, which led of improved air quality. This provides an opportunity to discuss the impact of human activities on air quality. [Objective] This study investigates the air quality changes in Shijiazhuang, and analyzes the impacts of epidemic prevention and control measures on air quality, so as to provide reference and ideas for further improving air quality and prevention and control measures. [Methods] The air quality data were collected online from https://www.zq12369.com/ and https://aqicn.org/city/shijiazhuang/cn/. Comparisons in air quality index (AQI) and the concentrations of air pollutants (PM2.5, PM10, SO2, CO, NO2, and O3) were made between the period from December 2019 to June 2020 (reference) and the same period from 2016 to 2019 by t-test and chi-square test. [Results] The daily average AQI dropped by 25.38% in Shijiazhuang during the COVID-19 prevention and control compared with the some period from 2016 to 2019 (t=6.28, P < 0.05). The proportions of pollution days during the COVID-19 outbreak in Shijiazhuang were PM2.5 (44.56%), O3 (31.09%), PM10 (23.83%), and NO2 (2.59%) successively, the pollution days of PM10 decreased significantly (chi2=3.86, P < 0.05) compared with 2016-2019, but during traffic lockdown the numbers of pollution days of PM2.5 and in the mid stage of prevention the number of pollution days of O3 increased (P < 0.05). Compared with the control period, the concentrations of the six air pollutants decreased to varying degrees (P < 0.05), especially SO2 dropped by 55.36%. [Conclusion] The measures taken for COVID-19 control and prevention have reduced the pollution sources and emissions, which resulted in better general air quality of Shijiazhuang City, but have aggravated the pollution of O3 and other pollutants. It is necessary to further explore the causes for the aggravation of O3 pollution in order to formulate reasonable air quality control strategies.Copyright © 2021, Shanghai Municipal Center for Disease Control and Prevention. All rights reserved.

COVID-19 and the Indoor Environment - observations from a joint National Academies of Engineering seminar series

The SARS-CoV-2 virus and its variants and COVID-19 disease have affected every aspect of society. The US National Academy of Sciences has been providing scientific insights and advice to aid policymakers and researchers in their quest to respond to the pandemic. Since 2020, it has produced numerous reports and workshop proceedings intended to integrate science into national preparedness and response decision-making, to explore lessons learned and best practices from previous preparedness and response efforts, and to consider strategies for addressing misinformation (NASEM, 2021). Among these was a 2021 symposium series that analyzed engineering's role in catalyzing COVID-19 response, recovery, and resilience, examining topics including the mitigation of exposure in public transit systems, engineering solutions to managing pathogens indoors, and the factors influence the transmission of infectious diseases in cities. Speaker presentations addressing these indoor environment topics are summarized here. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Examining the Association of Air Quality on Covid-19 Patient Outcomes Using Area Level Data from the Electronic Health Record

Background: Within the coronavirus 2019 (COVID-19) pandemic, literature has found worsened patient outcomes and increased virus transmissibility associated with reduced air quality. This factor, a structural social determinant of health (SDOH), has shown great promise as a link between air quality and patient outcomes during the COVID-19 pandemic. Researching SDOH within our patient populations is often difficult and limited by poor documentation or extensive questionnaires or surveys. The use of demographic data derived from the electronic health record (EHR) to more accurately represent SDOH holds great promise. The use of area-level determinants of health outcomes has been shown to serve as a good surrogate for individual exposures. We posit that an area level measure of air quality, the county-level Air Quality Index (AQI), will be associated with disease worsening in intensive care unit (ICU) patients being treated for COVID-19. Method(s): We will calculate AQI using a combination of open-source records available via the United States Environmental Protection Agency (EPA) and manual calculations using geospatial informatics systems (GIS) methods. Subjects will be identified as adult (> 18 years) patients admitted to Vanderbilt University Medical Center's ICUs between January 1, 2020, and March 31, 2022 with a positive SARS-CoV-2 laboratory analysis result. We will exclude patients without a home address listed. Patient demographic and hospital data from ICU admission to 28 days following admission will include: age, sex, home address, race, insurance type, primary language, employment status, highest level of education, and hospital course data. Together these will be collated to produce our primary outcome variable of WHO Clinical Progression Scale score. These validated scores range from 0 (uninfected) to 10 (dead) to track clinically meaningful progression of COVID-19 infected patients. Our AQI variable will be obtained from the EPA available county-level monitoring station spatial data combined with open-source state/county center point spatial data. These data contain historic cataloguing to determine air quality at both specific time points and averages over time. Where a county's average yearly AQI is not available due to lack of a monitoring station, we will use spatial data tools to calculate an average based on data from nearby stations. We will utilize yearly averages of AQI in the year prior to COVID-19 diagnosis to describe overall impact of air quality on patients' respiratory outcomes as opposed to single day exposures. Linkage of patient data to AQI database will be performed using patient addresses. Discussion(s): By combining area level data with electronic health record (EHR) data, we will be positioned to understand the contribution of environmental and social determinants of health on patient outcomes. Our long-term goal is to elucidate which social and environmental determinants of health are associated with worse outcomes from COVID-19 and other respiratory viruses, using data extracted from the EHR.

Can CO2 be used as an indicator of the probability of cross-infection?

The validity of using CO2 as an indicator of airborne infection probability was studied. Tracer gas measurements were conducted in a field lab with two breathing thermal manikins resembling "infected” and "susceptible” persons seated at desks. The room was ventilated with a mixing air distribution. Experiments were performed at three ventilation rates. CO2 gas was dosed into the air exhaled by the manikins to simulate the metabolic CO2 generation by people. Simultaneously, nitrous oxide (N2O) tracer gas was dosed into the air exhaled by one of the manikins ("infected person”) to simulate the emission of exhaled infectious particles. CO2 and N2O concentrations were measured at several points. The probability of infection was calculated based on the concentration of CO2 and N2O measured in the air inhaled by the exposed manikin ("susceptible person”). The results did not confirm that CO2 can be used as a proxy to assess the infection probability. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Key Elements Affecting the Library's CFU Concentration in Taiwan

Public libraries are popular gathering places, so understanding the factors that contribute to colony-forming unit (CFU) concentrations and how to minimize them is essential. This study aimed to investigate the factors that affect CFU concentrations in a public library, using air sampling (Bioluminescent ATP-assay) and statistical analysis software (SPSS) to collect and analyze data. The findings indicated that the CFU concentration in the library was significantly influenced by the air quality surrounding the building, the number of library visitors, and the hygiene and health of both visitors and employees. Additionally, indoor temperature and humidity were found to be key factors affecting CFU concentration. These findings suggest the need for better ventilation and air filtration systems, as well as regular cleaning and disinfection in public libraries. Furthermore, research is recommended to investigate other potential factors that may impact indoor air quality in public spaces.

Estimating SARS-CoV-2 infection risk in university dormitories using CO2 pulse injections

Air movement dynamics within three student dormitories were studied with simulated carbon dioxide (CO2) pulse injections to understand SARS-CoV-2 transmission risk. CO2 decay rate, proportion of shared air, and transport time were calculated from dynamic CO2 measurement data within simulated source and adjacent receptor rooms. Applying a Wells-Riley infection risk analysis with these results, the risk of SARS-CoV-2 infection in adjacent rooms ranged from 1% to 58% assuming an average emission rate of 5 quanta per hour and exposure duration of 3.5 days. Door opening status was very influential in resulting risk and vertical transport from source to above rooms was observed in all dormitories. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Carbon Dioxide Monitoring in Refuse Collection Vehicle Cabins to Reduce the Risk of SARS-CoV-2 Airborne Transmission

During the COVID-19 pandemic, essential workers such as waste collection crews continued to provide services in the UK, but due to their small size, maintaining social distancing inside waste collection vehicle cabins is impossible. Ventilation in cabins of 11 vehicles operating in London was assessed by measuring air supply flow rates and carbon dioxide (CO2) in the driver's cabin, a proxy for exhaled breath. The indoor CO2 indicated that air quality in the cabins was mostly good throughout a working day. However, short episodes of high CO2 levels above 1500 ppm did occur, mainly at the beginning of a shift when driving towards the start of their collection routes. This data indicated that the ventilation systems on the vehicles were primarily recirculating air and the fresh air supply made up only 10-20 % of the total airflow. Following recommendations to partly open windows during shifts and to maintain ventilation systems, a second monitoring campaign was carried out, finding on average, an improvement in ventilation on board the vehicles. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Post-Occupancy study of indoor air quality in university laboratories during the pandemic

This post-occupancy study aims to assess the indoor air quality (IAQ) and ventilation performance in workshops and laboratories of a UK university during the COVID-19 pandemic. Supply airflow rates and CO2 were monitored as a proxy for evaluating ventilation performance. Additionally, particulate matter (PM10) was monitored to address the occupant's concerns about dust. Monitoring showed that maximum CO2 values recorded are mostly below 1000 ppm, with weekly averages below 520 ppm. This was expected as the supply airflow rates were significantly larger than recommended 10 l/s per occupant. Despite the large flow rates, PM10 levels in some laboratories were above the threshold value of 50 [μg/m3] supporting the poor IAQ claims of the occupants. The study indicated the room air re-circulation and indoor activities as the likely reasons for the elevated PM10 levels and some practical operational solutions were suggested for IAQ concerns. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Transient zonal modeling of SARS-CoV-2 airborne infection risk for incomplete mixing air distribution methods

A widely used analytical model to quantitatively assess airborne infection risk is the Wells-Riley model based on the assumption of complete air mixing in a single zone. This study aimed to extend the Wells-Riley model so that the infection risk can be calculated in spaces where complete mixing is not present. This is done by evaluating the time-dependent distribution of infectious quanta in each zone and by solving the coupled system of differential equations based on the zonal quanta concentrations. In conclusion, this study shows that using the Wells-Riley model based on the assumption of completely mixing air may overestimate the long-range airborne infection risk compared to some high-efficiency ventilation systems such as displacement ventilation, but also underestimate the infection risk in a room heated with warm air supplied from the ceiling. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Upper-Room Germicidal Ultraviolet (UR-GUV) Application in High-Ceiling Indoor Settings for Disinfection of Airborne Viruses

This study investigated upper-room germicidal ultraviolet (UR-GUV) light application in a music rehearsal room with a high ceiling (7.5 m). The focus was on the influences of the elevation and height of UV zone on disinfection of airborne viruses. This study assumed a uniform UV fluence rate of 0.2 W/m2 in the UV irradiation zone. According to the Computational Fluid Dynamics (CFD) results, average viral concentrations (Ca), fraction remaining (FR), and equivalent air exchange rate (λe) attributed to GUV, have power relationships with UV zone height. Ca and FR decreased with UV zone height, while λe did the opposite. UV zone elevation showed little influence on UR-GUV performance, indicating well-mixed air in the rehearsal room. High ceiling makes it possible to achieve adequate UV dose by increasing both UV zone height and UV light intensity. Using open fixtures improved energy efficiency and reduced operational costs of the UR-GUV system. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Evaluation of airborne infection risk with different window airing strategies in classroom

The coronavirus disease may spread by airborne aerosols, especially in a poorly ventilated enclosure. Natural ventilation can reduce the transmission of infection. The WHO suggested the minimum ventilation rate of 10 L/s/person in non-residential settings. The objective was to evaluate risk of airborne infection with different settings in natural ventilated classroom. The risk was evaluated by using the modified Wells-Riley equation associated with the variation of contaminant concentration simulated by a multi-zone airflow model. The results provide the guidance of natural ventilation strategy in the classroom to reduce the transmission of airborne infection disease. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Multizone Modelling of SARS-CoV-2 Airborne Transmission in Mechanically Ventilated Buildings

This study contributes to a better understanding of the airborne transmission risks in multizone, mechanically ventilated buildings and how to reduce infection risk. A novel modeling approach combining the Wells-Riley and the US National Institute of Standards and Technology (NIST) CONTAM models was applied to a multizone whole building to simulate exposure and assess the effectiveness of different mitigation measures. A case study for the US Department of Energy large office prototype building was conducted to illustrate the approach. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Predicting the infection probability distribution due to airborne and droplet transmission

In this study, a method was proposed to predict the infection probability distribution rather than the room-averaged value. The infection probability by airborne transmission was predicted based on the CO2 concentration. The infection probability by droplet transmission was predicted based on occupant position information. Applying the proposed method to an actual office confirmed that it could be used for quantitatively predicting the infection probability by integrating the ventilation efficiency and distance between occupants. The infection probability by airborne transmission was relatively high in a zone where the amount of outdoor air supply was relatively small. The infection probability by droplet transmission varied with the position of the occupants. The ability of the proposed method to analyze the relative effectiveness of countermeasures for airborne transmission and droplet transmission was verified in this study. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Presence of SARS-CoV-2 in HEPA Filters of Portable Air Cleaners

A method for determining the presence of SARS-CoV-2 RNA in HEPA filters from portable air cleaners (PACs) have been developed and validated. Herein, a monitoring survey was conducted for 13 weeks in three indoor environments, school, nursery and a household of a socio-sanitary center in Ciudad Real, Spain. In this study, we employed environmental monitoring by RT-PCR of the presence of SARS-CoV-2 in HEPA filters and other surfaces of these indoor spaces for a selective screening in asymptomatic population groups. The aim was to limit outbreaks in an early stage. Only one HEPA filter tested positive in the socio-sanitary center. After analysis by RT-PCR of SARS-CoV-2 in residents and healthcare workers, one worker tested positive. Therefore, this study provides direct evidence of virus-containing aerosols trapped in HEPA filters and the possibility of using these PACs for environmental monitoring of SARS-CoV-2 while they remove airborne aerosols and trap the virus. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Development of an automatic window opening system to control the ventilation rate

Under the influence of COVID-19, it is recommended to ventilate to reduce the risk of infection in the room. In an air-conditioned room, window open can increased the ventilation rate that caused by indoor and outdoor temperature difference. However, there is a concern that opening window in the air-conditioned room will increase the heating and cooling load due to air leakage. In addition, it is difficult to maintain the appropriate ventilation rate because the outdoor air temperature changes time to time. To solve this problem, we have developed an automatic window opening system to control the natural ventilation rate. In this study, actual measurements were conducted to understand the operating performance of the system, and its effect on the indoor thermal environment. As a result, it was confirmed that the ventilation rate could be controlled by this system. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.