ASHRAE - American Society of Heating@ Refrigerating and Air-Conditioning Engineers@ Inc.
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ASHRAE IJHVAC 16-5-2010
Scope
INTRODUCTION Air movement in indoor environments is strongly linked to the transmission and spread of airborne infectious diseases@ such as measles@ tuberculosis@ chickenpox@ influenza@ smallpox@ and SARS (Li et al. 2007). The lack of knowledge of and insufficient data on ventilation requirements in hospitals@ schools@ and offices make it difficult to understand the spread of airborne infectious diseases (Li et al. 2007; Beggs et al. 2008). A study by Yin et al. (2009) showed that ventilation systems played a very important role in the transmission of exhaled particles from a patient to a caretaker in the same ward. They showed that displacement ventilation can provide much better indoor air quality than overhead mixing ventilation. The ventilation effectiveness of a displacement ventilation system with a reduced ventilation rate of 4 ach can be the same as that of an overhead mixing ventilation system with a ventilation rate of 6 ach. However@ there were concerns about whether an object moving@ such as a visitor or caretaker walking@ changing a sheet on the patient's bed@ or a swinging entrance door in an inpatient ward@ could destroy the stratified flow created by the displacement ventilation and thus decrease the ventilation effectiveness (Brohus et al. 2006; Bj?rn and Nielsen 2002; Bj?rn et al. 1997). Mazumdar (2009) found that a moving passenger in an aircraft cabin could carry a contaminant in his or her wake to positions far from the contaminant source. Thus@ it is essential to assess the impact of moving objects on contaminant transmission in inpatient wards with displacement ventilation.