Zhiwen Luo

Possible Role of Aerosol Transmission in a Hospital Outbreak of Influenza

Abstract Background. We examined the role of aerosol transmission of influenza in an acute ward setting. Methods. We investigated a seasonal influenza A outbreak that occurred in our general medical ward (with open bay ward layout) in 2008. Clinical and epidemiological information was collected in real time during the outbreak. Spatiotemporal analysis was performed to estimate the infection risk among patients. Airflow measurements were conducted, and concentrations of hypothetical virus-laden aerosols at different ward locations were estimated using computational fluid dynamics modeling. Results. Nine inpatients were infected with an identical strain of influenza A/H3N2 virus. With reference to the index patients location, the attack rate was 20.0% and 22.2% in the “same” and “adjacent” bays, respectively, but 0% in the “distant” bay (P=.04). Temporally, the risk of being infected was highest on the day when noninvasive ventilation was used in the index patient; multivariate logistic regression revealed an odds ratio of 14.9 (95% confidence interval, 1.7–131.3; P=.015). A simultaneous, directional indoor airflow blown from the “same” bay toward the “adjacent” bay was found; it was inadvertently created by an unopposed air jet from a separate air purifier placed next to the index patients bed. Computational fluid dynamics modeling revealed that the dispersal pattern of aerosols originated from the index patient coincided with the bed locations of affected patients. Conclusions. Our findings suggest a possible role of aerosol transmission of influenza in an acute ward setting. Source and engineering controls, such as avoiding aerosol generation and improving ventilation design, may warrant consideration to prevent nosocomial outbreaks.

Developing a research strategy to better understand, observe and simulate urban atmospheric processes at kilometre to sub-kilometre scales

A Met Office/Natural Environment Research Council Joint Weather and Climate Research Programme workshop brought together 50 key international scientists from the UK and international community to formulate the key requirements for an Urban Meteorological Research strategy. The workshop was jointly organised by University of Reading and the Met Office.

Ventilation in a street canyon under diurnal heating conditions

Abstract To study the thermal effects on airflow in a street canyon under real heating conditions (due to diurnal solar radiation), a one-way static approach combining an urban canopy model and CFD is proposed in this paper. An urban canopy model was developed to calculate the individual temperatures of surfaces in the street canyon. The calculated surface temperature may be used as a thermal boundary for CFD simulation. The reliability of this model was validated against a field experiment in Harbin, China. Using the coupling calculation method, the wind flow and air exchange process inside an idealized street canyon was studied. The simulation results show that the thermal effect has significant impacts on the transfer process in the street canyon, especially when the approaching wind is weak. Under a real diurnal thermal forcing, the flow structure within the street canyon changes from one primary vortex to two counter-rotating vortices. The change of transfer process, induced by the buoyancy force, was determined by the thermal condition of all surfaces rather than a single one.

Inhalation exposure to particulate matter in rooms with underfloor air distribution

This work investigated the personal exposure to indoor particulate matters using the intake fraction metric and provided a possible way to trace the particle inhaled from an indoor particle source. A turbulence model validated by the particle measurements in a room with underfloor air distribution (UFAD) system was used to predict the indoor particle concentrations. Inhalation intake fraction of indoor particles was defined and evaluated in two rooms equipped with the UFAD, i.e., the experimental room and a small office. According to the exposure characteristics and a typical respiratory rate, the intake fraction was determined in two rooms with a continuous and episodic (human cough) source of particles, respectively. The findings showed that the well-mixing assumption of indoor air failed to give an accurate estimation of inhalation exposure and the average concentration at return outlet or within the overall room could not relate well the intake fraction to the amount of particle emitted from an indoor source.

Health and economic benefits of building ventilation interventions for reducing indoor PM2.5 exposure from both indoor and outdoor origins in urban Beijing, China

China is confronted with serious PM2.5 pollution, especially in the capital city of Beijing. Exposure to PM2.5 could lead to various negative health impacts including premature mortality. As people spend most of their time indoors, the indoor exposure to PM2.5 from both indoor and outdoor origins constitutes the majority of personal exposure to PM2.5 pollution. Different building interventions have been introduced to mitigate indoor PM2.5 exposure, but always at the cost of energy expenditure. In this study, the health and economic benefits of different ventilation intervention strategies for reducing indoor PM2.5 exposure are modeled using a representative urban residence in Beijing, with consideration of different indoor PM2.5 emission strengths and outdoor pollution. Our modeling results show that the increase of envelope air-tightness can achieve significant economic benefits when indoor PM2.5 emissions are absent; however, if an indoor PM2.5 source is present, the benefits only increase slightly in mechanically ventilated buildings, but may show negative benefit without mechanical ventilation. Installing mechanical ventilation in Beijing can achieve annual economic benefits ranging from 200yuan/capita to 800yuan/capita if indoor PM2.5 sources exist. If there is no indoor emission, the annual benefits above 200yuan/capita can be achieved only when the PM2.5 filtration efficiency is no <90% and the envelope air-tightness is above Chinese National Standard Level 7. Introducing mechanical ventilation with low PM2.5 filtration efficiency to current residences in urban Beijing will increase the indoor PM2.5 exposure and result in excess costs to the residents.

30 minute averaged overview data from the Silsoe Refresh Cube Campaign (RCC)

All 30 minute averaged data taken during the Refresh Cube Campaign (RCC) at Silsoe using the 6 m^3 test structure at the site and eight other 6 m^3 straw cubes undertaken as part of the PhD work of Gough (2017) and forms the full-scale experiments of the REFRESH project. The data-set is split into two sections: an isolated cube and the array case with three different opening set-ups being undertaken for both array and isolated. The array was in place October 2014 to April 2015, and the cube was isolated from May 2015 to July 2015. Details of the experimental set-ups are available in publications. The data contained within this document are 30 minute averaged and quality controlled using code previously used for the ACTUAL project. The data set contains wind speeds, wind directions, internal and external temperatures, surface pressures, CO_2 concentrations and ventilation rates calculated from the pressure difference methods. Internal and external measurements are included for the flow.

Guest Editorial Ventilation for Healthy Indoor Environments in Various Types of Buildings Extended Papers from Indoor Air 2014

Exposure to air pollution from both outdoor and indoor origins can cause a myriad adverse health effects including cardiovascular and respiratory diseases, lung cancer and mortality. Approximately 3.7 million people worldwide died prematurely due to outdoor air pollution in 2012. As people spend more than 90% of their time indoors, the majority of exposure to outdoor air pollution actually occurs indoors, let alone the persistence of various indoor pollution sources indoors. Building ventilation has long been recognized as one of the most important engineering approaches to create a healthy indoor air environment. Therefore, ventilation research has been the significant component to the series of Indoor Air conferences dating from 1978 in Copenhagen, Denmark.

Effects of Urban Ventilation Patterns on the Carbon Monoxide Concentration in a High-Rise Mega City

Abstract Carbon monoxide (CO) concentration data from 1999–2006, monitored at 5 different pollution stations in a high-rise mega city (Hong Kong), were collected and investigated. The spatio-temporal characteristics of urban CO concentration profiles were obtained. A new approach was put forward to examine the relationship between urban CO concentration and different wind flow patterns. Rather than relying on the meteorological data from a single weather station, usually adopted in previous studies, four weather stations on the boundary of Hong Kong territory were used in the present study so as to identify 16 different wind flow patterns, among which a typical urban heat island circulation (UHIC) can be distinguished. Higher concentrations were observed to be associated with the flow pattern of an inflow from Lau Fau Shan (LFS) station which is located in the northwest of Hong Kong. This suggests that the ability of dilution for north-to-west wind is relatively weak due to the pollutants carried from outside Hong Kong. The effectiveness of wind speed on the alleviation of urban concentration is dependent on the initial concentration of the approaching wind. The increase of wind speed of north-to-west wind from 0 m/s to 6 m/s has little effect on the reduction of urban CO concentration, especially on the non-roadside stations. By contrast, for the southerly marine wind, pollution concentration decreases sharply with an increase in the wind speed. It was also found that urban heat island circulation (UHIC) is conducive of the accumulation of pollutants, especially at night. There exists a positive correlation between CO concentration and UHI intensity. This correlation is much stronger at night compared to during the day.