Search

We evaluated diurnal trends of size-resolved indoor and outdoor fluorescent biological airborne particles (FBAPs) and their contributions to particulate matter (PM) within 0.5-20 μm. After a ten-week continuous sampling via two identical wideband integrated bioaerosol sensors, we found that both indoor and outdoor diurnal trends of PM were driven by its bioaerosol component. Outdoors, the median [interquartile range] FBAP mass concentration peaked at 8.2 [5.8-9.9] μg/m3 around sunrise and showed a downtrend from 6:00 to 18:00 during the daytime and an uptrend during the night. The nighttime FBAP level was 1.8 [1.4-2.2] times higher than that during the daytime, and FBAPs accounted for 45 % and 56 % of PM during daytime and nighttime, respectively. Indoors, the rise in concentrations of FBAPs smaller than 1 μm coincided with the starting operation of the heating, ventilation, and air conditioning (HVAC) system at 6:00, and the concentration peaked at 8:00 and dropped to the daily average by noontime. This indicated that the starting operation of the HVAC system dislodged the overnight settled and accumulated fine bioaerosols into the indoor environment. For particles larger than 1 μm, the variation of mass concentration was driven by occupancy. Based on regression modeling, the contributions of indoor PM, non-FBAP, and FBAP sources to indoor mass concentrations were estimated to be 93 %, 67 %, and 97 % during the occupied period. National Research Foundation (NRF) Published version This research was funded by the Republic of Singapore's National Research Foundation through a grant to the Berkeley Education Alliance for Research in Singapore (BEARS) for the Singapore-Berkeley Building Efficiency and Sustainability in the Tropics (SinBerBEST) Program.

Background Multiple severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) superspreading events suggest that aerosols play an important role in driving the coronavirus disease 2019 (COVID-19) pandemic. To better understand how airborne SARS-CoV-2 transmission occurs, we sought to determine viral loads within coarse (>5 μm) and fine (≤5 μm) respiratory aerosols produced when breathing, talking, and singing. Methods Using a G-II exhaled breath collector, we measured viral RNA in coarse and fine respiratory aerosols emitted by COVID-19 patients during 30 minutes of breathing, 15 minutes of talking, and 15 minutes of singing. Results Thirteen participants (59%) emitted detectable levels of SARS-CoV-2 RNA in respiratory aerosols, including 3 asymptomatic and 1 presymptomatic patient. Viral loads ranged from 63–5821 N gene copies per expiratory activity per participant, with high person-to-person variation. Patients earlier in illness were more likely to emit detectable RNA. Two participants, sampled on day 3 of illness, accounted for 52% of total viral load. Overall, 94% of SARS-CoV-2 RNA copies were emitted by talking and singing. Interestingly, 7 participants emitted more virus from talking than singing. Overall, fine aerosols constituted 85% of the viral load detected in our study. Virus cultures were negative. Conclusions Fine aerosols produced by talking and singing contain more SARS-CoV-2 copies than coarse aerosols and may play a significant role in SARS-CoV-2 transmission. Exposure to fine aerosols, especially indoors, should be mitigated. Isolating viable SARS-CoV-2 from respiratory aerosol samples remains challenging; whether this can be more easily accomplished for emerging SARS-CoV-2 variants is an urgent enquiry necessitating larger-scale studies.

We conducted a prospective environmental surveillance study to investigate the air, surface, dust and water contamination of a room occupied by a patient infected with Monkeypox virus (MPXV) at various stages of his illness. The patient tested positive for MPXV from a throat swab and skin lesions. Environmental sampling was conducted in a negative pressure room with 12 unidirectional HEPA air changes per hour and daily cleaning of the surfaces. A total of 179 environmental samples were collected on days 7, 8, 13, and 21 of his illness. Air, surface, and dust contamination was highest during the first eight days of the illness, with a gradual decline to the lowest contamination level by day 21. Viable MPXV was isolated from surfaces and dust samples and no viable virus was isolated from the air and water samples.SynopsisInadequate research prevail on the mode of transmission for monkeypox virus. This study reports the findings of viable monkeypox virus from the patient environment, highlighting its implications for human health and impact on infection and prevention control measures.

SARS-CoV-2 has been recognized to be airborne transmissible. With the large number of reported positive cases in the community, home quarantine is recommended for the infectors who are not severely ill. However, the risks of household aerosol transmission associated with the quarantine room operating methods are under-explored. We used tracer gas technique to simulate the exhaled virus laden aerosols from a patient under home quarantine situation inside a residential testbed. The Sulphur hexafluoride (SF

The performance of a low-cost fan filter unit (FFU) in mitigating hazardous particulate matter (PM) levels in a naturally ventilated school classroom is presented. The FFU can be considered as a simplified mechanical ventilation and air-conditioning system without heating and cooling functions. The FFU improves indoor air quality through introduction of cleaned outdoor air to flush out internally generated heat and moisture and reducing infiltration by maintaining indoor pressurization. Indoor particle number concentrations were reduced between 85% and 95%. The particle removal performance (PRFFFU ) of the FFU is determined and incorporated into the augmented facade penetration factor (Paug ). A case-specific recursive dynamic mass balance model is used to characterize the infiltration factor (FINF ), deposition rate (K), and the penetration efficiency (Paug ) from continuously monitored indoor and outdoor mass concentration levels. Computed "Paug " (0.07, 0.09, and 0.13) and "FINF " (0.06, 0.08, and 0.11), respectively, for PM10, PM2.5, and PM1 suggest that exposure to PM was significantly reduced indoors. The effectiveness of the FFU for reduced "FINF " and "Paug " may be attributed to its superior filtration, dilution, and exfiltration mechanisms. In comparison with alternative PM mitigation solutions, the FFU is effective, affordable, and sustainable.

Data on the viral loads in respiratory aerosols from patients infected with Delta and Omicron variants are limited. In this study, we used an exhaled breath bioaerosol collector to collect aerosol samples in coarse (> 5µm) and fine (≤ 5µm) fractions from COVID-19 patients infected with these VOCs while doing various respiratory activities. Samples were tested via SARS-CoV-2 RT-qPCR and virus culture. Nine patients (4 Delta and 5 Omicron) were included. Viral RNA was detectable in seven participants, with greater viral loads in fine aerosols. Notably SARS-CoV-2 RNA was consistently detectable in respiratory samples of all Omicron patients despite them being fully vaccinated and mostly asymptomatic in contrast with Delta patients. Singing and talking without mask generated the greatest viral loads underscoring the transmission potential of SARS-CoV-2 and its variants via respiratory aerosols. The more consistent detection of viral RNA in Omicron-infected patients may account for its greater transmissibility.

There is great disparity in the way we think about and address different sources of environmental infection. Governments have for decades promulgated a large amount of legislation and invested heavily in food safety, sanitation, and drinking water for public health purposes. In contrast, airborne pathogens and respiratory infections, whether seasonal influenza or COVID-19, are ad-dressed fairly weakly, if at all, in terms of regulations, standards, and building design and operation, pertaining to the air we breathe. We suggest that the dramatic growth in our understanding of the mechanisms behind respiratory infection transmission should drive a paradigm shift in how we view and address the transmission of respiratory infections to protect present and future generations from unnecessary suffering and economic losses. It starts with a recognition that preventing respiratory infection, like reducing waterborne or food-borne disease, is a tractable problem. See Additional URL below for 'free to read' PDF reprint.

The utilization of physical dividers has been recommended as a practical approach to reducing the droplet and aerosol transmissions of the COVID‐19 virus (SARS‐CoV‐2). This study conducted a series of experiments using video recording with a high‐speed camera, particle image velocimetry (PIV) technique, and concentration measurements. The effectiveness of Perspex desk dividers impeding the transient transmission during coughing in five representative layouts was investigated. The results showed that the divider effectively protected the exposed person from an infector's cough seated in a face‐to‐face arrangement at a distance of 1.5 m. The aerosol concentration at the breathing zone was reduced by 99% compared to the layout without dividers. However, the reflection of aerosols from the dividers increased the exposure risk to the person seated beside the infector. Such risk was substantially reduced if the dividers were placed parallel between the infector and exposed person seated side‐by‐side. When the exposed person was staggered (face‐to‐face but displaced sideways laterally) to the infector with a 0.55‐m lateral distance, the dividers reduced the potential exposure at the breathing zone by 60%. Considering the effectiveness in exposure reduction, the staggered configuration of desk dividers between the infector and exposed persons offers the best reduction to exposure.

The effects of temperature, air movement and initial metabolic rate on transient thermal sensation at warm temperatures and high humidity among tropically acclimatized people were investigated. 26 tropically acclimatized subjects (13 males and 13 females) participated in the experiments with two different initial metabolic rates at temperatures of 24, 27 and 30 °C, relative humidity (RH) of 60% and air velocities ranging from 0.07 to 1.87 m/s. All the subjects participated in 18 sessions, each for 3.5 h. Thermal sensation in the first few minutes after entering the room moderated earlier with elevated air movement. Thermal sensation, thermal comfort and thermal acceptability reached steady-state within 15 and 25 min respectively at 27 and 30 °C with elevated air movement up to 1.87 m/s even at high initial metabolic rates. Air movement, temperature and initial metabolic rate had a great impact on immediate change in thermal sensation, comfort and acceptability after entry into an air-conditioned room from an outdoor environment. Thermal comfort was highly correlated with thermal sensation during the transient phase and it was observed that a much cooler thermal sensation than in steady-state was necessary for optimal thermal comfort during the transient state. When the initial metabolic rate decreased, the preferred thermal sensation for tropically acclimatized people showed a noticeable shift from cool (−1.87) to slightly cool (−0.77).

In a business as usual scenario, atmospheric carbon dioxide concentration (CO2) could reach 950 parts per million (ppm) by 2100. Indoor CO2 concentrations will rise consequently, given its dependence on atmospheric CO2 levels. If buildings are ventilated following current standards in 2100, indoor CO2 concentration could be over 1300 ppm, depending on specific ventilation codes. Such exposure to CO2 could have physiological and psychological effects on building occupants. We conducted a randomized, within-subject study, examining the physiological effects on the respiratory functions of 15 persons. We examined three exposures, each 150 min long, with CO2 of: 900 ppm (reference), 1450 ppm (decreased ventilation), and 1450 ppm (reference condition with added pure CO2). We measured respiratory parameters with capnometry and forced vital capacity (FVC) tests. End-tidal CO2 and respiration rates did not significantly differ across the three exposures. Parameters measured using FVC decreased significantly from the start to the end of exposure only at the reduced ventilation condition (p 2 alone and rather by other pollutants—predominantly human bioeffluents in this work—whose concentrations increased as a result.

During the rapid rise in COVID-19 illnesses and deaths globally, and notwithstanding recommended precautions, questions are voiced about routes of transmission for this pandemic disease. Inhaling small airborne droplets is probable as a third route of infection, in addition to more widely recognized transmission via larger respiratory droplets and direct contact with infected people or contaminated surfaces. While uncertainties remain regarding the relative contributions of the different transmission pathways, we argue that existing evidence is sufficiently strong to warrant engineering controls targeting airborne transmission as part of an overall strategy to limit infection risk indoors. Appropriate building engineering controls include sufficient and effective ventilation, possibly enhanced by particle filtration and air disinfection, avoiding air recirculation and avoiding overcrowding. Often, such measures can be easily implemented and without much cost, but if only they are recognised as significant in contributing to infection control goals. We believe that the use of engineering controls in public buildings, including hospitals, shops, offices, schools, kindergartens, libraries, restaurants, cruise ships, elevators, conference rooms or public transport, in parallel with effective application of other controls (including isolation and quarantine, social distancing and hand hygiene), would be an additional important measure globally to reduce the likelihood of transmission and thereby protect healthcare workers, patients and the general public.

Energy savings of the Air-Conditioning (AC) system is crucial in achieving energy conservation in buildings in the tropical region. A Dedicated Outdoor Air System with ceiling fans (DOAS-CF) aims to achieve energy savings arising from elevated room air temperature and minimizing the air-conditioning requirements. The objective of this study is to investigate the cooling effect produced by the DOAS-CF system at various locations in an AC room using a thermal manikin. The sedentary thermal manikin was set at three different locations such as under the ceiling fan, outside the fan blades and the center of the room at temperatures of 24 °C, 27 °C and 30 °C and at 60%RH with air velocities ranging from 0.02 m/s to 2.26 m/s at the height of 1.1 m. Two ceiling fans formed circulation airflows around each fan. High air speeds and low turbulence intensity were measured right under the ceiling fan and near the floor while low air speeds and high turbulence intensity were found at other locations. The cooling effect at the whole body of −3.3 °C was higher under the fan than that of −1.3 °C at other locations. The cooling effect was affected by temperature, location and fan speed mode significantly. The maximum cooling effect by manikin based equivalent temperature was higher than that by SET model due to an evaluation of the local cooling effect on each body part. The knowledge of the cooling effect is important and useful for a mechanical engineer to design the thermal environment produced by the DOAS-CF system.

Occupancy information is important to building facility managers in terms of building operation, predictive control, safety, as well as the indoor environment quality. Previous works have addressed different occupancy counting and estimation solutions in different buildings or spaces. In this study, we adopted a single system-single zone test bed using the existing university lecture rooms to install and compare four different occupancy counting methodologies: overhead video based occupancy counting system, pan-tilt-zoom camera face detection system, CO2-based physical model, and CO2-based statistical model. We attempt to address the occupancy counting challenge in educational building deployment scenario with large groups of people entering and leaving. Experiments have been conducted for three months with five-minute data reporting interval. The results show that the PTZ-camera based face recognition has the most stable and highest accuracy with an R2 of 0.972; followed by the CO2 based statistical model with an R2 of 0.938. Discussion and improvements on the methods are discussed. A final hybrid model is proposed by using the estimated occupancy by the PTZ face detection algorithm to train the CO2 model. This plug-and-play method overcomes the practical disadvantage of these two approaches, which also overcomes the main con of all of the methods that the modeling work is required before the technologies works.

Ventilation and air distribution methods are important for indoor thermal environments and air quality. Effective distribution of airflow for indoor built environments with the aim of simultaneously offsetting thermal and ventilation loads in an energy efficient manner has been the research focus in the past several decades. Based on airflow characteristics, ventilation methods can be categorized as fully mixed or non-uniform. Non-uniform methods can be further divided into piston, stratified and task zone ventilation. In this paper, the theory, performance, practical applications, limitations and solutions pertaining to ventilation and air distribution methods are critically reviewed. Since many ventilation methods are buoyancy driving that confines their use for heating mode, some methods suitable for heating are discussed. Furthermore, measuring and evaluating methods for ventilation and air distribution are also discussed to give a comprehensive framework of the review.

The effectiveness of a low energy fan-filter unit (FFU) in mitigating human exposure to airborne particulate matter (PM) during haze episodes in a naturally ventilated hostel room is presented. The study adopts a case-reference method by conducting a series of field tests in a test room equipped with FFU and in a reference room with no FFU. PM concentrations were monitored simultaneously indoors and outdoors; including mass concentrations of PM10, PM2.5 and PM1 as well as differential number concentrations of particles ranging from 0.35 μm to 12.5 μm. On average the FFU system reduced PM10, PM2.5, and PM1 particle concentrations by 80.9%, 80.4% and 78.5% respectively inside the test room relative to ambient air concentrations on a real-time comparison basis. The use of FFU operating with a MERV 13 filter during haze episodes is also effective in reducing human exposure to PM-bound toxic trace elements (TrElems) in naturally ventilated indoor environments. The majority of the TrElems (As, Be, Cd, Co, Cr, Ni, Pb, Mn, Zn and Cu) were reduced indoors with I/O ratio of much less than 1. Additionally, FFU demonstrates slight alleviation of thermal discomfort compared to the reference room (whose windows and doors were closed to prevent penetration of haze particles) and achieves thermal conditions within the 80%–90% in the adaptive thermal comfort zone described in ASHRAE Standard 55–2013. The improved thermal conditions with FFU is attributable to provision of increased air exchange (ACH of 4.1 h−1) to displace the indoor generated heat and moisture.

Air conditioning and mechanical ventilation systems may be oversized in commercial buildings in the Tropics. Oversized cooling coils may lead to reduced dehumidifying performance, indoor air quality and thermal comfort and increased energy consumption. In this paper, an adaptable cooling coil design is assessed with a general-purpose coil selection software tool, in which the number of active rows changes as a function of the load. For a 100% oversized coil, it is shown that the adaptable cooling coil is able to provide small but relevant improved humidity control down to 25% of the design load. This was obtained without affecting energy performance in typical variable air volume design and control. For specific applications, where variable air volume systems mainly control space humidity, there are also energy savings. The adaptable cooling coil could be seen as providing additional flexibility in the operation of HVAC systems, particularly in the tropics.

Several relationships between air temperature and work performance have been published. We reanalysed the one developed in 2006 by Seppänen et al.; which is probably the best known. We found that even when significant, its prediction accuracy is very low (R2 = 0.05, MAE = 1.9%, RMSE = 3.1%). We consequently reviewed the literature and found 35 studies on the effects of temperature on office work performance. We used Seppänen et al.’s approach to normalise the data reported in these studies and explored the feasibility to develop a new relationship using regression models, models based on the Maximal Adaptability framework, and machine learning. We could not find a relationship between temperature and office work performance neither for the range of temperatures measured in most of the office buildings (20 °C–30 °C) or a wider range (18 °C–34 °C). Plausible reasons are discussed including the variety of methods used to assess performance, the multiple uncontrolled confounders, and the fact that temperature alone may not fully describe how the thermal environment affects building occupants. We do not recommend the use in practice of any of the models relating temperature to office work performance examined in the present study. The lack of relationships does not necessarily refute that temperature affects the performance of office work. Coordinated research predicated on a shared protocol enabling integrated analysis in the modelling of the relationships between the indoor thermal environment and office work performance is proposed to be carried out before using them in practice. We made the database open-source and developed an application for data exploring.

Assessment of integrated personal exposure (PE) to airborne particulate matter (PM) across diverse microenvironments (MEs) over 24 hours under different exposure scenarios is necessary to identify appropriate strategies to improve urban air quality and mitigate the health effects of PM. We carried out a collaborative study in a densely populated city-state (Singapore) to assess the integrated PE to fine particles (PM2.5), ultrafine particles (UFPs) and black carbon (BC) across diverse indoor and outdoor urban MEs, estimate related health risks and make suitable recommendations for healthy living in cities. Two volunteers with different lifestyles participated in the study by tracking their PE to particulate air pollution and the time-activity patterns over 24 hours using portable PM monitoring devices and recording their whereabouts using GPS coordinates. Home, transport and recreation (i.e., food court) MEs represented pollution hotspots of PM2.5 (21.0 μg/m3), BC (3.4 μg/m3) and UFP (33.0 × 103 #/cm3), respectively. Among the different modes of transport used by the participants (walking, cycling, e-scooter, mass rapid transport (MRT), bus, car and taxi), the air pollutants had elevated concentrations while commuting by public transport (bus and MRT) as well as during active modes of transport (walking and cycling). Air-conditioned cars and taxis, equipped with air filtration systems, represented the lowest PE. The health risk assessment revealed that there are potential carcinogenic risks associated with the long-term exposure to elevated levels of PM2.5-bound toxic trace elements. These risks can be mitigated with the introduction of low-carbon and active modes of transport in place of internal combustion engines and the use of indoor air pollution exposure mitigation devices.

Indoor airborne transmission largely depends on air distribution and ventilation. This study experimentally and numerically investigates steady-state aerosol transmission characteristics in a full-size room using a dedicated outdoor air system coupled with ceiling fans. Tracer gas was used to simulate the exhaled droplet nuclei from the infector, and a breathing thermal manikin was employed as a seated exposed person. Effects of air supply rates, ceiling fan speeds, source positions, and breathing modes of the exposed person on the aerosol transmission were studied. The increase of air change per hour from 4.5 to 5.6 and 7.5 reduced the averaged concentrations at sampling points by 18% and 38%, respectively. The ceiling fans generated local air movement and mixed air within the space, and a higher operating speed contributed to a more uniform concentration distribution. With better dispersion of the aerosols, the ceiling fan operation reduced the concentrations at the exposed person's breathing zone by more than 20%. The ceiling fans show the potential to reduce the cross-infection risk in an air-conditioned space.

The combustion of fossil fuels is a significant source of particulate-bound black carbon (BC) in urban environments. The personal exposure (PE) of urban dwellers to BC and subsequent health impacts remain poorly understood due to a lack of observational data. In this study, we assessed and quantified the levels of PE to BC under two exposure scenarios (home-based and mobility-based exposure) in the city of Trivandrum in India. In the home-based scenario, the PE to BC was assessed in a naturally ventilated building over 24 h each day during the study period while in the mobility-based scenario, the PE to BC was monitored across diverse microenvironments (MEs) during the day using the same study protocol for consistency. Elevated BC concentrations were observed during the transport by motorcycle (26.23 ± 2.33 µg/m3) and car (17.49 ± 2.37 µg/m3). The BC concentrations observed in the MEs decreased in the following order: 16.58 ± 1.38 µg/m3 (temple), 13.78 ± 2.07 µg/m3 (restaurant), 11.44 ± 1.37 µg/m3 (bus stop), and 8.27 ± 1.88 µg/m3 (home), the standard deviations represent the temporal and spatial variations of BC concentrations. Overall, a relatively larger inhaled dose of BC in the range of 148.98–163.87 µg/day was observed for the mobility-based scenario compared to the home-based one (118.10–137.03 µg/day). This work highlights the importance of reducing PE to fossil fuel-related particulate emissions in cities for which BC is a good indicator. The study outcome could be used to formulate effective strategies to improve the urban air quality as well as public health.

Energy consumption and indoor environment quality (IEQ) of buildings have been linked to human occupants. Predicting the number of occupants in a space is essential for the effective management of various building operation functions as well as improve energy efficiency. This study is the first to compare the performance of physical and statistical models in predicting occupant counts in a high volume lecture theatre (Occ = 200) using CO 2 sensors. CO 2 measurements and actual occupant numbers were obtained for 4 months to provide robust data comparison of the methodologies. It was found that that the dynamic physical models and Support Vector Machines (SVM) and Artificial Neural Networks (ANN) models utilizing a combination of average and first order differential CO 2 concentrations performed the best in terms of predicting occupancy counts with the ANN and SVM models showing higher predictive performance. RMSE values for the corresponding models were 12.8, 12.6 and 12.1 respectively and correlation coefficients were all greater than 0.95. The relatively good agreement between dynamic physical model predictions and ground truth shows that the dynamic mass balanced model is adequate for predicting occupancy counts provided that the air exchange rates measured are accurate. Model average accuracies across all tolerance was between 70 and 76% demonstrating good performance for a large number of occupants. A discussion on the merits and limitations of each model types was presented to provide guidance on the adoption of various models.

The anthropogenic heat, which primarily consists of emissions from human metabolism, and also the rejected or waste heat from electricity consumption in buildings due to human activities and the requirement for maintaining the thermal environment by human being, is considered as an important contributor to the urban heat island phenomenon and has been studied worldwide. High energy consumption in the urban buildings impacts the urban surface energy budget and causes the emission of anthropogenic heat flux into the atmosphere. Today, with the growing population and growing activities in buildings, much of the concern is focused towards the decrease of anthropogenic heat through low energy consuming and more energy efficient buildings. This study, utilized a validated occupancy probabilistic input model to estimate different building retrofitting solutions on the impact of building energy consumption and further as the basis for building cooling associated anthropogenic heat study. A holistic evaluation of passive, active and combined strategies is tailored for application with high occupancy variation situation such as campus buildings. With the best retrofitting solutions, the campus anthropogenic heat is reduced from 150 W/m2 to 128 W/m2, which is considered as very effective. Although the campus buildings are used as an example, this paper demonstrates a generalisation method for the application of retrofitting strategies and efficient building systems in estimating the reduction of anthropogenic heat. The results demonstrate high potential for the campus building retrofitting and the values can contribute as a database for future urban heat island effect estimation.

Clustering algorithms have been successfully applied in analyzing building energy consumption data. It has proven to be an effective technique to identify representative energy consumption patterns as well as being a pre-processing step for other techniques. In this paper, we propose a clustering method based on k-shape algorithm, which is a relatively novel method to identify shape patterns in time-series data. In the experiment, clustering is performed for each individual building according to its hourly consumption. The novelty of this paper is that a new k-shape algorithm is applied to detect building-energy usage patterns at different levels, and the clustering result is further utilized to improve the accuracy of forecasting models. Ten institutional buildings covering three different typologies are used as case studies and a set of hourly and weekly energy consumption data is further analyzed in this paper. The experimental results reveal that this proposed method can detect building energy usage patterns in different time granularity effectively and also proves that the forecasting accuracy of SVR model is significantly improved by utilizing the results of the proposed clustering method.

Author(s): Li, Jiayu; Wan, Man Pun; Schiavon, Stefano; Tham, Kwok Wai; Zuraimi, Sultan; Xiong, Jinwen; Fang, Mingliang; Gall, Elliott | Abstract: This study evaluated the interrelations between indoor and outdoor bioaerosols in a bedroom under a living condition. Two wideband integrated bioaerosol sensors were utilized to measure indoor and outdoor particulate matter (PM) and fluorescent biological airborne particles (FBAPs), which were within a size range of 0.5-20 μm. Throughout this one-month case study, the median proportion of FBAPs in PM by number was 19% (5%; the interquartile range, hereafter) and 17% (3%) for indoors and outdoors, respectively, and those by mass were 78% (12%) and 55% (9%). According to the size-resolved data, FBAPs dominated above 2 and 3.5 μm indoors and outdoors, respectively. Comparing indoor upon outdoor ratios among occupancy and window conditions, the indoor FBAPs larger than 3.16 μm was dominated by indoor sources, while non-FBAPs were mainly from outdoors. The occupant dominated the indoor source of both FBAPs and non-FBAPs. Under awake and asleep, count- and mass-based mean emission rates were 45.9 and 18.7 × 106 #/h and 5.02 and 2.83 mg/h, respectively. Based on indoor activities and local outdoor air quality in Singapore, this study recommended opening the window when awake and closing it during sleep to lower indoor bioaerosol exposure.

Field surveys were carried out to evaluate the thermal comfort, perceived air quality (PAQ) of occupants and energy consumption in two different spaces of an actual university building, one of which is equipped with a Dedicated Outdoor Air System integrated with ceiling fans (DOAS-CF) and the other equipped with a conventional Fan Coil Unit (FCU). A total of 244 subjects (65 males and 179 females) responded to questionnaires in a design studio operated with DOAS-CF at a warmer setpoint temperature of 27 °C and a computer lab operated with FCU at a setpoint temperature of 24 °C (which is common for the Tropics). Occupants under DOAS-CF at 27 °C felt more thermally comfortable and expressed higher thermal acceptability than those under FCU at 24 °C through their behavioral adjustment in choosing their sitting location based on their thermal and air movement preferences. With DOAS-CF, the cooling experienced by the nose has favorably inclined the olfactory sense towards PAQ; however, there is a small percentage who felt the PAQ was unacceptable as they were also thermally uncomfortably warm. Energy consumption of DOAS-CF was 27.7% lower than that of FCU due to warmer setpoint temperature. Despite creating a wide range of effective temperatures, DOAS-CF system can achieve better thermal comfort when occupants’ behavioral adaptation is empowered; it also achieves higher energy conservation by increasing setpoint temperature than the conventional mixing AC system.

Understanding occupants’ satisfaction with their environment is an important step to improve indoor environmental quality (IEQ). These satisfaction data are limited to Singaporean commercial buildings. We surveyed (N = 666) occupant satisfaction with 18 IEQ parameters in seven Green Mark certified air-conditioned commercial buildings in Singapore. About 78% of the participants expressed satisfaction with their overall workspace environment. Occupants were most satisfied with flexibility of dress code (86% satisfaction), electrical lighting (84%) and cleanliness (82%), and most dissatisfied with sound privacy (42% dissatisfaction), personal control (32%) and temperature (30%). We found that satisfaction with cleanliness has the highest impact to overall workspace environment satisfaction. Our results suggest achieving high occupant satisfaction for some IEQ factors is harder than others, which suggests the premise of singular satisfaction rating (e.g., 80%) that applies to all IEQ parameters may not be reliable and representative. We determined that the major contributors to thermal dissatisfaction were insufficient air movement and overcooled workspaces. Occupants in open plan office were unhappy with the noise produced by their nearby colleagues. We also found that several IEQ variables (odors, air movement, available space, overall privacy, sound privacy and temperature) which are not statistically significant to the overall workspace satisfaction on their own, but their impacts becomes substantial when these IEQ variables are merged into larger environmental factors (i.e., Perceived Air Quality, Acoustics, Layout and Thermal). These results can support the development of an IEQ benchmarks for commercial buildings in Singapore.

A reflective approach is adopted in analyzing the reviews on the impact of indoor air quality on humans over the last 30 years (1986–2016). The major findings reiterate the concerns of indoor air pollution (IAP) and provide a deeper understanding of how contaminants contribute to, and interact to accentuate the adverse effects on humans. Issues which have emerged and increased in importance are indoor chemistry, airborne infection, and the impact on performance. Societal trends of rising affluence of the middle class, increased population density in cities, introduction of new synthetic materials, reliance on childcare facilities have led to greater intensity of exposure to IAP. Responses to climate change, energy conservation and singular strategies to manage the complex challenge of IAP have not been effective in alleviating the deterioration of indoor air quality. Innovations in air distribution, air cleaning, modularization of indoor environmental devices/systems, and leveraging on smart technologies and sensing systems which incorporate algorithms that optimizes indoor air quality with conventional performance indicators are important advancements towards a holistic solution. User engagement, both as a sensor and indicator of preferences, when integrated with such innovations, may usher in the next important paradigm towards achieving acceptable indoor environmental quality beyond the current definitions of acceptability from population-based criteria to one that embraces the individual on an as-needed, when-needed and as-preferred basis.

Energy management in offices requires efficient methods (e.g. non-intrusive load monitoring techniques, NILM) to monitor the large number of workstations and office appliances. The key purpose of this study is to ascertain the applicability of using time series subsequence data mining to study and classify the transient operations of typical appliances in an office. The approach involves discovering hidden subsequences (i.e. feature extraction) that are characteristic of individual appliance transient states, using an extension of Symbolic Aggregate approXimation (SAX). Such characteristic features are used to create a repository of rules to help supervised classification of aggregate time series measurements. It is one of the first studies to demonstrate the potential of classifying subsequence features into individual appliances and their states within large aggregate time series data using a “Bag of Rules” approach. The results indicate that distinct, characteristic patterns represent office appliances and their states, in the form of SAX grammar rules. These patterns can then be used for NILM with promising results. This ongoing study demonstrates SAX based time series subsequence mining as a proof-of-concept; not only to discover similarities presented by appliance events but also to demonstrate their applicability to disambiguate aggregate signatures in the context of office NILM.

High temperature cooling is gaining more attention in commercial buildings of the tropical climates where temperature and humidity is high all year round. In this air-water system, radiant-convective cooling is provided into conditioned space through using higher chilled water temperature compared to conventional all air system. Radiant cooling panel, radiant slab cooling, passive/active chilled beams are the main design strategies for implementing this concept into buildings. This paper reviewed and summarized the recent published papers on applications of high temperature cooling systems in tropical buildings. The reported outcomes and conclusions from these studies were extracted and discussed to get a better understanding on overall performance of the systems which are designed based on this concept. The potential energy saving of this strategy was estimated to be in the range of 6–41% depending on design strategies and operational scenarios of system. Comfortable and healthy indoor environment is achievable for this design when a parallel air system satisfies latent load and ventilation requirement of space. Low air movement was the only reported comfort concern for this design since locally acclimatized occupants in the tropics prefer higher air movement compared to dry and temperate climates. Regarding the parallel air system strategy, DOAS with ceiling supply-ceiling exhaust is suggested to be the best choice to be coupled with high temperature cooling system. In addition, incorporation of energy recovery systems like membrane based air to air heat exchanger into DOAS can improve the overall efficiency of this design.