Influence of a portable air cleaner location on the exposure to exhaled contaminants in hospital rooms

Abstract

Indoor environments with a deficient mechanical ventilation, could increase exposure to exhaled contaminants. This situation is critical in hospital environments such as hospital rooms. In this situation, a portable air cleaner system based on high efficiency air filters maybe a solution by itself or combined with mechanical ventilation systems to reduce the concentration of aerosols in hospital room environments. In this study the influence of the location of a portable air cleaner based on high efficiency air filters on the exposure to exhaled contaminants of a health worker close to a patient lying on a bed was investigated. The experimental setup consists of a hospital room (40.84 m3) with two breathing thermal manikins, BTM. One BTM was lying on the bed (patient) and the other BTM was stand up near the bed (health worker). Each BTM has its own independent breathing system with the capability of performing different breathing flows. Both BTM inhale and exhale through the mouth with a respiration frequency of 17.90 min-1 (inhalation) and 16.43 min-1 (exhalation). Both has minute volume 9.46 (l/min) and tidal volume 0.55 l. The BTM lying on a bed, simulated the source of exhaled contaminants and exhales particles sized 0.57-0.76 μm. A total air flow rate of 150 m3/h (3.67 ACH) was used in all experimental tests. The total air flow rate was generated only by the air cleaner, only by the ventilation system or using a combination of the air cleaner and the ventilation system. The concentration of particles was measured in the inhalation of the standing BTM close to bed, and in other points of the room to analyse the influence of air cleaner location on the exposure to airborne contaminants. The results suggest that the air diffusion plays an important role in the exposure to exhaled contaminants in a hospital room. In these indoor environments, low values in the exposure to exhaled contaminants can be obtained using a combination of a portable air cleaner located near the source of contaminants and the ventilation system or using only 100% air flow rate in the ventilation system.