Abstract
ABSTRACT In a ward where many patients are hospitalized, effective ventilation is important because airborne viruses may cause secondary infection. This study investigates the changes in the air quality in a four-bed ward according to the use of a ventilation system (VS), an air cleaner (AC), a system air conditioner (SAC), and personal curtains. The age of air was obtained both experimentally and numerically, and used as an indicator for the ventilation efficiency assessment. Consequently, the air flows from the outlets of the four-way cassette SAC could interfere with or contribute to the introduction of fresh air depending on the positions in the ward. For positions where the fresh air could not reach easily when only the VS was used, the air quality was improved by the additional use of the SAC. While the use of personal curtains prepared for each bed interfered with the air flow in the ward and resulted in local spots with poor air quality, the operation of both the VS and the SAC enhanced the air flow and improved the local air quality. The overall indoor air quality was improved when the AC was used. However, the ventilation efficiency was reduced when the SAC was operated along with the AC, and the air quality deteriorated at positions where the flow caused by the SAC and that by the AC interfered with each other.
Highlights
Most patients in need of long-term treatment are hospitalized
This study investigated the effect of the flow caused by the operation of the four-way cassette system air conditioner (SAC) installed on the ceiling of the ward on the indoor air quality
Considering the situation of the ward, the changes in the age of air at seven positions were examined at the height (0.85 m from the floor) of the nose of a patient lying in the bed according to the operation of the SAC
Summary
Most patients in need of long-term treatment are hospitalized. If some of the hospitalized patients are infectious virus carriers, secondary infection may occur to other patients in the ward because of airborne viruses (Beggs, 2003). Qian et al (2010) conducted field tests to investigate natural ventilation for reducing airborne infection in hospital wards They found that the air change rate reached up to 69 air changes per hour (ACH) and concluded that natural ventilation could reduce cross-infection of airborne diseases. Adamu et al (2012) evaluated four natural ventilation strategies for a single-bed hospital ward They found that ceiling-based natural ventilation was helpful for enhancing air quality at isolated parts of the ward. Gilkeson et al (2013) investigated local ventilation rates by applying a pulse-injection gas tracer method to assess potential infection risk in large naturally ventilated hospital wards. They found that indoor ventilation rates in a cross-ventilated ward increased with local external wind speed, leading to 3.4–6.5 ACH
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