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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.
This special issue presents a selection of extended papers of relevance to ventilation research that were presented at the Indoor Air 2014 conference which was held in Hong Kong between 7 to 12 July 2014. It contains 8 papers that address recent advancements in the field of building ventilation to achieve a healthy indoor environment for different types of buildings. Ventilation requirements vary significantly for different types of buildings ranging from dwellings to healthcare settings. Each paper in this issue is devoted to a better understanding of ventilation design in a specific indoor environment.
In this edition Kalliomaki et al experimentally studied the airflow patterns and air exchange volume through single hinged and sliding doors in a full-scale hospital isolation room. Smoke visualization was applied to show the airflow pattern and tracer gas measurement was used to quantify the air exchange flow volume. Their experimental results showed that a sliding door can generate notably smaller and tardy flow compared to a hinged door. The exchange volume was found to range between 0.3 m3 - 2.3 m3 with a sliding door and between 1.2 m3 - 2.4 m3 with a hinged door. Continuing this theme Hathway et al presented a novel study on air exchange and infection transfer due to hinge-door motion in both office and hospital environments. They first conducted field measurements and water tank experiments to quantify the volume of air exchange due to door motion. The infection risk due to infectious substances being transferred between rooms by door opening was finally evaluated.
Hellwig et al specifically looked at how to improve air quality in classrooms by reactivating historic ventilation stacks. Their measurements demonstrated that the airflow rate per person would be approximately seven times higher compared to the classroom with window only ventilation during winter periods. Kalamees et al also considered the retrofit of manor schools in which the environmental air quality was poor due to the inadequate performance of ventilation and heating systems. In particular these poor conditions were considered to have an adverse influence on the performance of school work. The original natural ventilation and window airing approach was found not to be a suitable solution with natural airflow being considerably lower than in classrooms with mechanical exhaust ventilation.
Laverge et al considered ventilation and IAQ in low-energy residential buildings in Belgium. They measured and compared the CO2 and humidity levels in 36 old, 39 standard and 39 low energy dwellings in Belgium. Their results showed that the risk of exposure to high carbon dioxide concentrations in the bedroom is about 6 times higher than that in the living room. Airtight buildings combined with a mechanical ventilation system can provide good IAQ in comparison with the leaky buildings but the operation of mechanical ventilation is a problem in practice.
Ai and Mak compared the single-sided natural ventilation characteristics for both single-storey and multi-storey buildings using CFD. Their simulation results showed that a more complex flow pattern was expected for multi-storey buildings, and that empirical models developed for single-sided single-storey buildings cannot be applied to multi-storey buildings. It calls for a future study to develop a more generalized single-sided natural ventilation model.
Yang and Gao examined gaseous pollutant transport driven by stack effect in a high-rise residential building in Shanghai using a multi-zone airflow model. Their simulation results indicated that the temperature difference and the location of the pollutant source had the most significant impacts on pollutant concentration in the flats above the neutral pressure level (NPL). Opening windows frequently was recommended to reduce the airborne infection risk in high-rise buildings.
As a special type of building, the emergency temporary housing built after the Great East Japan Earthquake was investigated by Honma, focusing on the effects of ventilation on hygrothermal behaviour. Both field measurement and numerical simulation were employed. This is extremely important in relation to understanding and solving condensation problems in order to improve indoor air quality.